To determine the prevalence of anti–high-density lipoprotein (anti-HDL) antibodies and to establish a possible relationship between anti-HDL, anticardiolipin antibodies (aCL), anti–β2-glycoprotein I (anti-β2GPI), and paraoxonase (PON) activity in patients with systemic lupus erythematosus (SLE) and primary antiphospholipid syndrome (APS).
Thirty-two patients with SLE and 36 with primary APS were enrolled in a cross-sectional study. Twenty age- and sex-matched healthy subjects were used as controls. Serum levels of IgG and IgM aCL, anti-β2GPI, and antiprothrombin antibodies and IgG anti-HDL were measured by enzyme-linked immunosorbent assay. Total cholesterol, HDL cholesterol, HDL2, and HDL3 were determined by standard enzymatic techniques. PON activity was assessed by quantification of nitrophenol formation, and total antioxidant capacity (TAC) by chemiluminescence.
Levels of total HDL, HDL2, and HDL3 were reduced in patients with SLE compared with controls (mean ± SD 0.51 ± 0.3, 0.37 ± 0.3, and 0.14 ± 0.1 mmoles/liter, respectively, versus 1.42 ± 0.9, 1.01 ± 0.7, and 0.40 ± 0.2). Patients with SLE and primary APS had higher titers of anti-HDL antibodies and lower PON activity than controls. In the SLE population, PON activity was inversely correlated with IgG anti-HDL titers (r = −0.48, P = 0.005) whereas in the primary APS population, IgG anti-β2GPI was the only independent predictor of PON activity (r = −0.483, P = 0.003). In the SLE group, anti-HDL was inversely correlated with TAC (r = −0.40, P < 0.02), and PON activity was positively correlated with TAC (r = 0.43, P < 0.02).
IgG anti-HDL and IgG anti-β2GPI antibodies are associated with reduced PON activity in patients with SLE and primary APS. Since the physiologic role of PON is to prevent low-density lipoprotein oxidation with its attendant atherogenic effects, the reported interactions may be relevant to the development of atherosclerosis in SLE and primary APS.