Browsing by Author "Sini, S"

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    Evidence for an exclusive association of matrix metalloproteinase-9 with dysfunctional high-density lipoprotein: A novel finding
    (Atherosclerosis, 2014-09) Sini, S; Deepa, D; Harikrishnan, S; Jayakumari, N
    OBJECTIVE: High-density lipoprotein is a heterogeneous class of lipoprotein with diverse antiatherogenic functions. However, these antiatherogenic properties of HDL can be compromised in atherosclerotic conditions. We have recently identified dysfunctionality in HDL even among healthy subjects, during systemic inflammation. This study was carried out with the objective of examining whether dysfunctional HDL is associated with pro-inflammatory proteins other than the acute phase proteins as reported earlier. METHODS: Serum HDL was isolated by three different methods-density gradient ultracentrifugation, PEG precipitation and electroelution. The antioxidant property of HDL was assessed as change in oxidation of LDL based on Dichloro-dihydro-fluorescein diacetate assay. HDL was subjected to gelatin zymography and western blot for assessment of MMP 9 activity. RESULTS: Dysfunctional HDL did not prevent the auto-oxidation of LDL. On the contrary the oxidation was enhanced. The zymogram data indicated enhanced MMP-9 activity selectively in dysfunctional HDL, irrespective of HDL isolation methods. This was confirmed by western blot of HDL probed with antibody specific to MMP 9. We also observed that dysfunctional HDL induced inflammatory response in monocyte/macrophages as evidenced by enhanced TNF-α and decreased IL-10 production. Further, invitro incubation of functional HDL with MMP-9 provided direct evidence for the association of MMP-9 with HDL and the role of MMP-9 in HDL dysfunction. CONCLUSION: A remarkable finding in the present study is the previously unrecognized association of MMP-9 with dysfunctional HDL and its proinflammatory property, indicating a novel molecular connection that can enhance the risk of cardiovascular disease in subjects with dysfunctional HDL.
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    Functionally defective high density lipoprotein is Pro-Oxidant: a Deviation from Normal Atheroprotective Character
    (International Journal of Nutrition and Food Sciences., 2013-02) Sini, S; Jayakumari, N
    High-density lipoprotein is a potential life saving antiatherogenic molecule. However, not all HDL is functionally similar, it can become dysfunctional and may increase atherosclerotic risk. At present, it is unknown, which structural alterations of HDL are essential accounting for its defective functionality and the precise pro-atherogenic mechanisms of action. This study is aimed at identification of the possible prevalence of dysfunctional HDL in subjects and its compositional and functional characterization in comparison to that of functional HDL. HDL was isolated from serum by ultracentrifugation and subjected to functional assays. HDL from majority of healthy subjects showed remarkable antioxidant property by inhibiting LDL oxidation. However, in those healthy subjects with systemic oxidative stress and inflammatory response as well as in those with known coronary heart disease, HDL was dysfunctional and promoted LDL oxidation. Dysfunctional HDL was truly pro-oxidant as it induced intracellular reactive oxygen species formation in cultured monocytes/macrophages. Functional deficiency in HDL did not show any association with HDL-cholesterol content. However, its characterization showed an enrichment of triglycerides, phospholipids, lipid peroxides, and diminished activity of paraoxonase-1, compared to functional HDL, which might render the particle dysfunctional and pro-oxidant.This study demonstrates the prevalence of dysfunctional HDL even among healthy subjects, despite normal HDL-C level, and in majority of subjects with known CHD, which is pro-oxidant in nature that might promote vascular inflammation and atherogenesis. The functional assay of HDL could lead to improved predictive accuracy of cardiovascular disease risk associated with circulating HDL.