Quantitation of plasminogen epitopes of serum lipoprotein(a) by sandwich enzyme linked immunosorbent assay

Percutaneous coronary intervention results in acute increases in native and oxidized lipoprotein(a) in patients with acute coronary syndrome and stable coronary artery disease

OBJECTIVE

To investigate possible changes of native and oxidized lipoprotein(a) [ox-Lp(a)] levels after percutaneous coronary intervention (PCI).

DESIGN AND METHODS

Lp(a), ox-Lp(a), and Lp(a) immune complexes (IC) and autoantibody levels were studied in 111 patients with acute coronary syndrome (ACS) and 68 patients with stable coronary artery disease (CAD) before and after PCI.

RESULTS

Compared with pre-PCI, Lp(a), ox-Lp(a), and Lp(a)-IC levels acutely increased, while the autoantibody decreased in both the ACS and stable CAD patients. They all returned toward baseline by 1 to 2 days. The absolute change of ox-Lp(a) was found positively related with both the diameter of stenosis (R=0.273, P=0.004) and the number of vessel disease (R=0.312, P=0.001) in the ACS patients, while not in the stable CAD patients.

CONCLUSION

PCI results in acute plasma increases of ox-Lp(a) and Lp(a). Ox-Lp(a) may be present in ruptured or permeable plaques and be released into the circulation by PCI.

Elevated concentrations of oxidized lipoprotein(a) are associated with the presence and severity of acute coronary syndromes

OBJECTIVE

To investigate possible mechanisms and association of increased oxidized Lp(a) [ox-Lp(a)] levels with presence and extent of acute coronary syndromes (ACS).

METHODS

Ox-Lp(a) levels were studied in 96 patients with ACS, 89 patients with stable coronary artery disease (CAD), and 100 control subjects.

RESULTS

Compared to control, ox-Lp(a) levels increased in stable CAD patients (P<0.001), and especially in ACS (P<0.001) (ACS, 16.29+/-13.80 microg/ml; stable CAD, 10.04+/-10.32 microg/ml; control, 7.10+/-9.16 microg/ml). The ratio of ox-Lp(a) to Lp(a) was higher in the ACS than those in the stable CAD (P<0.05) and control (P<0.001). Ox-Lp(a) levels were found associated with a graded increase in extent of angiographically documented CAD in the ACS (R=0.275, P=0.007), while not in the stable CAD (R=0.090, P=0.402). Multiple linear regression analysis found ox-Lp(a) (beta=0.271, P=0.019), age (beta=0.244, P=0.038) and TG (beta=0.213, P=0.070) accounted for 11.1% of the variation in the extent of angiographically documented CAD in ACS patients; Lp(a) (beta=0.415, P=0.000) and extent of CAD (beta=0.193, P=0.071) accounted for 21.5% of that in ox-Lp(a) levels.

CONCLUSION

Elevated ox-Lp(a) levels are associated with presence and severity of ACS, and may be useful for identification of patients with ACS.

Plasma oxidized lipoprotein(a) and its immune complexes are present in newborns and children

BACKGROUND

Oxidized Lp(a) [ox-Lp(a)] has been reported to play more potent roles than native Lp(a) in atherosclerosis. We investigated the distribution characteristics of plasma ox-Lp(a) and Lp(a) immune complex [Lp(a)-IC] levels in newborns and children.

METHODS

Plasma ox-Lp(a) and Lp(a)-IC levels were measured in 747 children and 30 cord blood by ELISAs.

RESULTS

The mean levels of Lp(a), ox-Lp(a) and Lp(a)-IC were much lower in newborns than in children (P<0.001), and increased rapidly to that in children after birth. The distributions of Lp(a), ox-Lp(a) and Lp(a)-IC were skewed toward low values in children, no difference of their levels was found in each of the 13year groups. The levels of ox-Lp(a) correlated positively with total and LDL cholesterol, Lp(a) and Lp(a)-IC; Lp(a)-IC correlated positively with sex, total and LDL cholesterol, Lp(a) and ox-Lp(a), respectively. Multiple linear regression analysis showed Lp(a) and Lp(a)-IC accounted for 42% of the variation in ox-Lp(a) levels, and ox-Lp(a) accounted for 30% of that in Lp(a)-IC.

CONCLUSIONS

The fact that ox-Lp(a) and Lp(a)-IC are present in newborns and children suggests that oxidized lipoproteins play an initiating role in atherosclerotic process.

Native, oxidized lipoprotein(a) and lipoprotein(a) immune complex in patients with active and inactive rheumatoid arthritis: plasma concentrations and relationship to inflammation

BACKGROUND

Several studies suggest that lipoprotein (a) [Lp(a)] act as acute phase reactant and be associated with early atherosclerosis in rheumatoid arthritis (RA). Oxidized Lp(a) [ox-Lp(a)] and Lp(a) immune complex (IC) concentrations both increased in patients with coronary heart disease. We investigated Lp(a), ox-Lp(a) and Lp(a)-IC concentrations in RA patients and to explore the relationships with inflammatory disease activity markers.

METHODS

Plasma Lp(a), ox-Lp(a) and Lp(a)-IC concentrations, and inflammatory markers were analyzed in 54 patients with RA, including 23 active and 21 inactive RA, and 60 control subjects.

RESULTS

Lp(a) and ox-Lp(a) concentrations in active RA were higher than those in both inactive RA and control; Lp(a)-IC concentrations in active RA were also higher than inactive RA, while no difference was found in Lp(a), ox-Lp(a) and Lp(a)-IC concentrations between inactive RA and control. Lp(a) concentrations were found positively correlated with ox-Lp(a) and Lp(a)-IC concentrations, respectively; ox-Lp(a) concentrations were also related with Lp(a)-IC. Lp(a), ox-Lp(a) and Lp(a)-IC were all found positively related with C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), respectively.

CONCLUSIONS

Native, oxidized Lp(a) and Lp(a)-IC concentrations increased in active RA patients. Inflammation may induce the changes of Lp(a), resulting in increased ox-Lp(a) and Lp(a)-IC, and may play an important role in atherosclerosis.

Development of new enzyme-linked immunosorbent assay for oxidized lipoprotein(a) by using purified human oxidized lipoprotein(a) autoantibodies as capture antibody

BACKGROUND

Oxidized Lp(a) [ox-Lp(a)] has been reported to play more potent role than native Lp(a) in atherosclerosis. Ox-Lp(a), autoantibodies, and Lp(a) immune complexes have all been detected in vivo. Thus, the isolation of its autoantibodies and the investigation of ox-Lp(a) may provide a new means to explore the exact pathogenic role of ox-Lp(a). We isolated and identified human autoantibodies against ox-Lp(a) and developed a new ELISA for ox-Lp(a) by using autoantibodies as capture antibody.

METHODS

Ox-Lp(a) autoantibodies were isolated and identified from healthy subjects by affinity chromatography. 2 "sandwich" ELISAs were developed for measuring ox-Lp(a) level, using autoantibodies against ox-Lp(a) or rabbit antiserum against ox-LDL as the capture antibody and quantitating with monoclonal anti-apo(a) enzyme conjugate, respectively. Ox-Lp(a) levels were studied by both the ELISAs in 100 patients with coronary heart disease (CHD) and 100 control subjects.

RESULTS

The isolated ox-Lp(a) autoantibodies reacted with both apo(a) and apoB epitopes of Ox-Lp(a). Compared to control, plasma ox-Lp(a) levels in patients with CHD were significantly increased (ELISA using human autoantibodies: 24.3+/-33.4 vs. 8.4+/-9.3 microg/ml, P<0.0001; ELISA using antibodies against ox-LDL: 13.0+/-13.8 vs. 7.3+/-9.7 microg/ml, P<0.0001, respectively). Furthermore, a significantly positive relationship between ox-Lp(a) levels detected by 2 ELISAs was also found (R=0.78, P<0.0001).

CONCLUSION

We isolated human autoantibodies against ox-Lp(a), which can recognize both apo(a) and apoB epitopes of ox-Lp(a). The developed ELISA for ox-Lp(a) by using human auoantibodies may more accurately reflect the state of Lp(a) oxidation in vivo. Ox-Lp(a) levels increase in patients with CHD.

Detection of IgG-bound lipoprotein(a) immune complexes in patients with coronary heart disease

BACKGROUND

LDL-immune complexes (IC) have a powerful pathogenic role for inducing foam cell formation in vitro more efficiently than any other known mechanism. Studies have also shown that plasma LDL-IC concentration is a powerful marker for the development of atherosclerosis. The structure, fatty acid composition and antioxidant concentrations of Lp(a) and LDL are quite similar. The same oxidation pattern has also been described for both lipoproteins. Modified forms of Lp(a), some resembling oxidized Lp(a), have been identified in human atheromatous lesions. The existence of autoantibodies against MDA-Lp(a) in vivo is also presented. Therefore, we suppose that Lp(a) might trigger an immune response leading to the production of autoantibodies and subsequently to the formation of immune complexes. This study examined the existence of IgG-bound Lp(a)-IC and investigated its value as a risk factor for the development of atherosclerosis.

METHODS

We developed two "sandwich" ELISAs for measuring plasma Lp(a)-IC and LDL-IC concentrations, using anti-human IgG(Fab) as the capture antibody, and quantitating with monoclonal anti-apo(a) or anti-apoB enzyme conjugate. Their concentrations were studied in 160 patients with coronary heart disease (CHD) and 290 control subjects.

RESULTS

Plasma TC, LDL-C, TG and apoB concentrations in CHD patients were all significantly increased, whereas HDL-C and apoAI concentrations were decreased. The Lp(a) concentrations in the patients with CHD were also significantly different from those of control (262.4+/-220.0 vs. 211.3+/-199.4 mg/l, P<0.005). Plasma Lp(a)-IC (2.24+/-1.71 vs. 1.62+/-1.50 AU, P<0.0001) and LDL-IC (2.77+/-1.29 vs. 1.40+/-0.92 AU, P<0.0001) concentrations in patients with CHD were both significantly higher than those of control. The relationships between Lp(a)-IC, LDL-IC concentrations and other lipid traits in all the studied subjects (n=450) were carried out. LDL-IC concentrations were positively correlated with LDL-C, apoB, TC, TG and Lp(a) concentrations, while negatively correlated with HDL-C and apoAI concentrations, respectively. Similarly, Lp(a)-IC concentrations were positively correlated with Lp(a), LDL-C, apoB and TC concentrations, while negatively correlated with HDL-C and apoAI concentrations, respectively. Furthermore, a significantly positive relation between LDL-IC and Lp(a)-IC concentrations was also found (r=0.313, P<0.0001).

CONCLUSIONS

We report the existence of Lp(a)-IC in both the plasma of patients with CHD and control subjects. Lp(a)-IC concentration increases in the CHD patients.