OBJECTIVETo detect the methylation status of p16 gene promotor in DNA derived from plasma and blood cells of patients with systemic lupus erythematosus (SLE) , and it's relationship with clinical symptoms.

METHODSp16 promotor methylation in plasma and peripheral blood cells (PBCs) DNA were simultaneously detected with the methylation specific PCR (MSP) method in 24 active SLE patients, 21 inactive SLE patients, as well as 20 healthy controls.

RESULTSIn the plasma DNA, p16 gene methylation ratio (MP%) was higher in SLE patients than in the healthy controls (64.4% vs. 5.0%, P < 0.05). MP% in the active SLE patients was significantly higher than that in the inactive SLE patients (83.3% vs. 42.9%, P < 0.05). In the PBCs, p16 gene methylation ratio (MC%) in the healthy controls was significantly higher than that in SLE (80.0% vs. 48.9%, P < 0.05). MC% in the active SLE patients (29.2%) was the lowest among three groups. There was no significant difference between the inactive SLE patients and healthy controls (71.4% vs. 80.0%, P > 0.05). Each patient could be judged as one of the four methylation patterns: MP/MC, UP/MC (UP: unmethylated plasma p16) , MP/UC (UC: unmethylated PBCs p16) , and UP/UC. The ratios of MP/ MC and UP/UC were similar between the active and inactive SLE patients. However, different distributions of other two patterns were found in the active and inactive SLE patients as UP/MC 4.2% vs. 42.9% (P <0.05) and MP/UC 58.3% vs. 14.3% (P < 0.05), respectively. The active SLE patients with MP/UC and the inactive SLE patients with UP/MC showed different clinical symptoms and laboratory examinations. Significant correlation was found between the disease activity index for lupus patients (SLEDAI) scores and MP% (r = 0.93), between the SLEDAI scores and MC% (r = - 0.96) also between MC% and MP% (r = - 0.79).

CONCLUSIONThe p16 methylation assay provides available information for the diagnosis, judgment of disease activity, as well as novel insights into the pathogenesis underlying this disease.