Cholesterol efflux via HDL resecretion occurs when cholesterol transport out of the lysosome is impaired.

Recently, we showed that holo HDL particle uptake and resecretion occur in physiologically relevant cell lines and that HDL uptake is mediated by scavenger receptor class B type I (SR-BI). Furthermore, we established that HDL resecretion is accompanied by [(3)H]cholesterol efflux. This study shows that HDL uptake and resecretion occur even when LDL uptake and cholesterol trafficking are disturbed.

A Chinese hamster ovarian cell line imports cholesterol by high density lipoprotein degradation.

Plasma high density lipoprotein (HDL) is inversely associated with the development of atherosclerosis. HDL exerts its atheroprotective role through involvement in reverse cholesterol transport in which HDL is loaded with cholesterol at the periphery and transports its lipid load back to the liver for disposal. In this pathway, HDL is not completely dismantled but only transfers its lipids to the cell.

Redox-sensitive impairment of porcine coronary artery vasodilation by hypochlorite-modified LDL.

Atherosclerotic vascular disease is associated with abnormal vasomotor function and oxidized low density lipoproteins (OxLDL) are believed to play a keyrole therein. Several compounds emerging from LDL lipid peroxidation have been shown to be able to alter vasomotion but the role of oxidized apoB in this process is not fully understood. Myeloperoxidase has been identified in atherosclerotic lesions and hypochlorite produced by this enzyme represents a strong oxidant.

SR-BI-mediated high density lipoprotein (HDL) endocytosis leads to HDL resecretion facilitating cholesterol efflux.

The high density lipoprotein (HDL) receptor, scavenger receptor class B, type I (SR-BI), mediates selective cholesteryl ester uptake from lipoproteins into liver and steroidogenic tissues but also cholesterol efflux from macrophages to HDL. Recently, we demonstrated the uptake of HDL particles in SR-BI overexpressing Chinese hamster ovarian cells (ldlA7-SRBI) using ultrasensitive microscopy. In this study we show that this uptake of entire HDL particles is followed by resecretion.

Products of the reaction of HOCl with tryptophan protect LDL from atherogenic modification.

Hypochlorite (HOCl) attacks amino acid residues in LDL making the particle atherogenic. Tryptophan is prone to free radical reactions and modification by HOCl. We hypothesized, that free tryptophan may quench the HOCl attack therefore protecting LDL.

Free zinc inhibits transport of vitamin C in differentiated HL-60 cells during respiratory burst.

Zinc is an essential trace element for the immune system. It is known to be essential for highly proliferating cells, especially for cells of the immune system. However, zinc and other divalent cations are known to inhibit the human neutrophilic NADPH oxidase.

Sulfite facilitates LDL lipid oxidation by transition metal ions: a pro-oxidant in wine?

Lipid oxidation in LDL may play a role in atherogenesis. It has been shown that sulfite - a compound in the aqueous fraction of wine - could inhibit free radical (AAPH) mediated oxidation of plasma. Thus, sulfite has been proposed as an antioxidant.

Intravenous iron preparations and ascorbic acid: effects on chelatable and bioavailable iron.

Background: There is growing interest to use ascorbic acid as adjuvant therapy for patients with recombinant human erythropoietin-hyporesponsiveness (rHuEpo). Several clinical studies showed the beneficial effect of ascorbic acid treatment on hematologic parameters in rHuEpo-treated hemodialysis patients with elevated or even normal iron stores. However, whether ascorbic acid directly affects stability and cellular metabolism of intravenous iron preparations (IVI) is not well understood.

Hypericin and photodynamic treatment do not interfere with transport of vitamin C during respiratory burst.

Hypericin is a photosensitizing pigment found in St. John's wort (Hypericum perforatum) displaying a high toxicity towards certain tumors. The fact that some non-tumor cells, especially monocytes and granulocytes, are resistant to its photocytotoxic effects, posed the question whether this insensitivity is due to their ability to accumulate vitamin C, an antioxidant which alleviates the deleterious work of free radicals.