Contribution of an adenine to guanine single nucleotide polymorphism of the matrix metalloproteinase-13 (MMP-13) -77 promoter region to the production of anticyclic citrullinated peptide antibodies in patients with HLA-DRB1*shared epitope-negative rheumatoid arthritis.

We examined whether matrix metalloproteinase-13 (MMP-13) contributes to disease susceptibility or severity of rheumatoid arthritis (RA). Eighty-seven patients with RA whose disease duration was <2 years and 71 healthy controls were enrolled in the study. Adenine (A) to guanine (G) single nucleotide polymorphism (SNP) of the -77 MMP-13 promoter region in RA and healthy controls was determined by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) technique. Human leukocyte antigen (HLA)-DRB1 genotyping was also performed using the same populations. Anticyclic citrullinated peptide (anti-CCP) antibodies from RA patients at entry were studied, and their relationships were examined. The genotype and allele frequency of SNP of MMP-13 at -77 did not differ between RA patients and healthy controls. We focused on the RA patients who were negative for HLA-DRB1*shared epitope (SE) alleles and found that the seropositivity of anti-CCP antibodies with a titer >25 U/ml was high in the A/A genotype compared with the G/G genotype. The same characteristic was also found in HLA-DRB1*0405 allele-negative patients. Our data suggest that SNP of the -77 MMP-13 promoter region acts as a surrogate marker of anti-CCP antibody production in HLA-DRB1*SE allele-negative RA patients, which may reflect RA severity.