Involvement of HNP-1 in different oxidation mechanisms in human endothelial cells

Native low density lipoprotein promotes lipid raft formation in macrophages

Oxidized low-density lipoprotein (LDL) has an important role in atherogenesis; however, the mechanisms underlying cell-mediated LDL oxidation remain to be elucidated. The present study investigated whether native-LDL induced lipid raft formation, in order to gain further insight into LDL oxidation. Confocal microscopic analysis revealed that lipid rafts were aggregated or clustered in the membrane, which were colocalized with myeloperoxidase (MPO) upon native LDL stimulation; however, in the presence of methyl-β-cyclodextrin (MβCD), LDL-stimulated aggregation, translocation, and colocalization of lipid rafts components was abolished.. In addition, lipid raft disruptors MβCD and filipin decreased malondialdehyde expression levels. Density gradient centrifugation coupled to label-free quantitative proteomic analysis identified 1,449 individual proteins, of which 203 were significantly upregulated following native-LDL stimulation. Functional classification of the proteins identified in the lipid rafts revealed that the expression levels of translocation proteins were upregulated. In conclusion, the results of the present study indicated that native-LDL induced lipid raft clustering in macrophages, and the expression levels of several proteins were altered in the stimulated macrophages, which provided novel insights into the mechanism underlying LDL oxidation.

Leukocyte and leukocyte subset counts reveal compensatory mechanisms in coronary heart disease

BACKGROUND

Leukocyte number in the circulation plays a central role in inflammatory diseases, such as coronary heart disease (CHD). Increased counts are correlated with the intensity of the peri-infarction inflammatory response and adverse outcomes. We investigated leukocyte and leukocyte subset counts in dyslipidaemia patients and their relationship with LDL oxidation.

METHODS

Dyslipidaemia patients (207) were selected for blood counts and LDL-C testing. The level of HNP-1and myeloperoxidase in subsets of leukocytes and their relationship with LDL oxidation were compared between 24 CHD patients and 24 normal controls.

RESULTS

In dyslipidaemia patients, total leukocyte and neutrophil counts increased with LDL-C (p=0.001). Monocyte counts showed the opposite trend (p=0.001). Although serum HNP-1 levels were not different between CHD patients and normal controls (p=0.558), neutrophil HNP-1 mRNA levels were 2.13-fold greater than those of normal controls. However, monocyte HNP-1 mRNA levels were lower (p=0.005). The distribution of myeloperoxidase in monocytes and neutrophils is different, myeloperoxidase locates mainly in the cytoplasm of monocytes, on the cell membrane of neutrophils.

CONCLUSIONS

Leukocyte and leukocyte subset counts may correlate with LDL-C levels and LDL oxidation. The monocyte-neutrophil interaction reveals a potential compensatory mechanism associated with LDL oxidation in CHD that may be a prognostic factor of CHD.