TBPP_The ins and outs of HDL

apoA-1: 70% of HDL protein, import to cholesterol efflux, activates LCAT, anti-oxidant and anti-inflammatory, mostly in spherical HDL. / apoA-2: 20% of HDL, function unknown, increases stability, mostly in spherical HDL / apoA-4: minor, similar function to apoA-1, 1/2 spherical HDL, 1/2 in lipid-free form / apoA-V: minor, metabolism of triglyceride rich lipoproteins / apoE: minor, involved in cholesterol efflux, for recognition of HDL by cell receptors, mostly HDL. / apoC-1/2/3: minor, metabolism of triglyceride rich lipoproteins / apoD, apoJ, apoL, apoM: minor, functions unknown

main layer, aphipatic helices: one side charged (affinity for aqueous phase), other side hydrophobic (binding to lipid), 2 regions joined by hinge (plastic, several formations possible), 1 g/L

HDL smallest and densest lipoproteins of plasma, heterogeneous with many subpopulations (different shapes, sizes, densities, composition, surface charges), 2 major subpopulations: apoA1 but no apoA2, both apoA1 and apoA2

all starts in liver and intestine by secretion of a lipid poor protein (apoA-1), through ABCA1 receptors, phospholipids and cholesterol quickly acquired: pre-Beta discoidal HDLs. Cholesterol in discoidal HDL is esterfied by LCAT. The cholesterin-esters arent water soluble and move inside of the particle to form a lipid core. change of pre-beta to alpha spherical particles. larger spherical can also be remodelled to smaller sizes by cholesterol-esters and triglyceride depletion. Some apo-A1 lost during the process and can pick up new phospholipids and cholesterol from cell membranes (discoidal HDLs)

ATP-binding cassette A1/G1 (ABCA1/G1): moves cholesterol to poor apoA-1/spherical HDLs, scavenger receptor type B (SR-B1): in liver, selectively takes cholesterol from HDLs, Lecithin (Cholesterol Acyltransferase LCAT): catalyses esterification of cholesterol in HDL (80% esterfied), Cholesteryl ester transfer protein (CETP): redistributes cholesterolesters and triglycerides between HDLs and triglyceride-rich lipoproteins. phospholipid transfer protein (PTLP): transfer phosholipids between HDLs and other lipoproteins, Hepatic Lipase (HL): resides on surface of liver cells, substrate: HDL triglyceride. Lipoprotein Lipase (LPL): on cell surface, hydrolyses triglycerides. Endothelial Lipase (EL): on cell surface, substrate: HDL phospholipid.

plasma cholesterol transport and unrelated to cholesterol transport

movement of cholesterol from extrahepatic tissues back to the liver, 4 distinct processes. ABCA1: efflux of cholesterol from cells to lipid poor apoA-1. ABCG1: efflux of cholesterol from cells to large spherical HDLs. SR-B1: bidirectional transfer of cholesterol between cells and spherical HDLs, only if LCAT-mediated concentration gradient. passive diffusion: of cholesterol to spherical HDLs, if LCAT-mediated concentration gradient.

cholesterol efflux from macrophages in the artery wall, antioxidative activity, vasodilatory activity, promote angiogenesis, endothelial repair amd improved function, antithrombic activity, antidiabetic activity, anti-inflammatory activity

fractions: VLDL, CM, IDL, LDL, HDL, VHDL, PLFF, high density lipoproteins at the bottom, HDL in the middle, fractions separated by chromatography and/or PAGE. apoA-1 isolated from plasma typically comes out of fraction IV, content: 2%, more than one way, CSL: resuspension in EtOH --> filtration --> IP --> filtration --> dissolution and clearfiltration --> pathogen safety steps --> UF/DF --> lipid/cholate addition --> reconstituted HDL --> final formulation, sterile filtration, lyophilization. Reconstitution: cholate detergent method (dialysis or affinity), homogenization, thermal cycling (just add lipid)

multiple sclerosis, sepsis, arthritis, diabetes, drug delivery system, cancer, artherosclerosis and cardiovascular disease (heart attack)

Acute Coronary Syndrome ACS impairs cholesterol efflux in HDL subfractions. Infusion of reconstituted HDL leads to acute changes in cholesterol plaques (CSL111 not erased --> CSL112), CER-001 fails to regress: increase in cholesterol mobilization but didnt reduce coronary artherosclerosis.