Patients with Rheumatoid Arthritis Show Altered Lipoprotein Profiles with Dysfunctional High-Density Lipoproteins that Can Exacerbate Inflammatory and Atherogenic Process

Abstract

Objective: In order to identify putative biomarkers in lipoprotein, we compared lipid and lipoprotein properties between rheumatoid arthritis (RA) patients and control with similar age.

Methods: We analyzed four classes of lipoproteins (VLDL, LDL, HDL2, HDL3) from both male (n = 8, 69±4 year-old) and female (n = 25, 53±7 year-old) rheumatoid arthritis (RA) patients as well as controls with similar age (n = 13).

Results: Although RA group showed normal levels of total cholesterol (TC), low-density lipoprotein (LDL)-cholesterol, and glucose, however, the RA group showed significantly reduced high-density lipoprotein (HDL)-C level and ratio of HDL-C/TC. The RA group showed significantly elevated levels of blood triglyceride (TG), uric acid, and cholesteryl ester transfer protein (CETP) activity. The RA group also showed elevated levels of advanced glycated end (AGE) products in all lipoproteins and severe aggregation of apoA-I in HDL. As CETP activity and TG contents were 2-fold increased in HDL from RA group, paraoxonase activity was reduced upto 20%. Electron microscopy revealed that RA group showed much less HDL2 particle number than control. LDL from the RA group was severely oxidized and glycated with greater fragmentation of apo-B, especially in female group, it was more atherogenic via phagocytosis.

Conclusion: Lipoproteins from the RA patients showed severely altered structure with impaired functionality, which is very similar to that observed in coronary heart patients. These dysfunctional properties in lipoproteins from the RA patients might be associated with high incidence of cardiovascular events in RA patients.

Fig 1

Expressional level of IL-6 in equally diluted serum (20 μg/lane) as visualized by immunodetection (A) Lower numbers indicate band intensity from Chemi-Doc analysis. Glycation extent of LDL based on fluorescence determination (B) and electrophoretic profiles of LDL as visualized by Coomassie Brilliant Blue staining (C). CM, control male; RAM, rheumatoid arthritis male; CF, control female; RAF, rheumatoid arthritis female.

Fig 2. Comparison of LDL oxidation susceptibility by determination of conjugated dienes (A) and Comparison of electromobility of LDL between with or without cupric ion in 0.5% agarose gel (B).

CM, control male; RAM, rheumatoid arthritis male; CF, control female; RAF, rheumatoid arthritis female.

Fig 3. Glycation extent of HDL based on fluorescence determination (A) and electrophoretic profiles of HDL as visualized by Coomassie Brilliant Blue staining (B).

CM, control male; RAM, rheumatoid arthritis male; CF, control female; RAF, rheumatoid arthritis female.

Fig 4. HDL₃ associated cholesteryl ester transfer protein (CETP) activity (A) and paraoxonase (PON) activity (B).

CM, control male; RAM, rheumatoid arthritis male; CF, control female; RAF, rheumatoid arthritis female.

Fig 5

Uptake of LDL from each group into macrophages was visualized by Oil-red O staining to detect fatty acid and triglyceride (A). Immunodetection of phospho-IκB in cell lysate of the macrophages. Lower numbers indicate band intensity from Chemi-Doc analysis (B). Beta actin was immunodetected as a internal standard. CM, control male; RAM, rheumatoid arthritis male; CF, control female; RAF, rheumatoid arthritis female.

Fig 6. Uptake of LDL from each group into macrophages was visualized by fluorospectroscopy to detect NBD-cholesterol.

CM, control male; RAM, rheumatoid arthritis male; CF, control female; RAF, rheumatoid arthritis female.

Fig 7. Representative photo of negatively-stained HDL₂ from RA patients and controls (electron microscopy).

All micrographs are shown at a magnification of 40,000×. The scale bar corresponds to 100 nm. Graphs show measured particle size and number from designated area. CM, control male; RAM, rheumatoid arthritis male; CF, control female; RAF, rheumatoid arthritis female.