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Eugene A Podrez - One of the best experts on this subject based on the ideXlab platform.
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cross linking modifications of hdl Apoproteins by oxidized phospholipids structural characterization in vivo detection and functional implications
Journal of Biological Chemistry, 2020Co-Authors: Detao Gao, Mohammad Z Ashraf, Lifang Zhang, Niladri Kar, Tatiana V Byzova, Eugene A PodrezAbstract:Apolipoprotein A-I (apoA-I) is cross-linked and dysfunctional in human atheroma. Although multiple mechanisms of apoA-I cross-linking have been demonstrated in vitro, the in vivo mechanisms of cross-linking are not well-established. We have recently demonstrated the highly selective and efficient modification of high-density lipoprotein (HDL) Apoproteins by endogenous oxidized phospholipids (oxPLs), including γ-ketoalkenal phospholipids. In the current study, we report that γ-ketoalkenal phospholipids effectively cross-link Apoproteins in HDL. We further demonstrate that cross-linking impairs the cholesterol efflux mediated by apoA-I or HDL3 in vitro and in vivo Using LC-MS/MS analysis, we analyzed the pattern of Apoprotein cross-linking in isolated human HDL either by synthetic γ-ketoalkenal phospholipids or by oxPLs generated during HDL oxidation in plasma by the physiologically relevant MPO-H2O2-NO2- system. We found that five histidine residues in helices 5-8 of apoA-I are preferably cross-linked by oxPLs, forming stable pyrrole adducts with lysine residues in the helices 3-4 of another apoA-I or in the central domain of apoA-II. We also identified cross-links of apoA-I and apoA-II with two minor HDL Apoproteins, apoA-IV and apoE. We detected a similar pattern of Apoprotein cross-linking in oxidized murine HDL. We further detected oxPL cross-link adducts of HDL Apoproteins in plasma and aorta of hyperlipidemic LDLR-/- mice, including cross-link adducts of apoA-I His-165-apoA-I Lys-93, apoA-I His-154-apoA-I Lys-105, apoA-I His-154-apoA-IV Lys-149, and apoA-II Lys-30-apoE His-227. These findings suggest an important mechanism that contributes to the loss of HDL's atheroprotective function in vivo.
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characterization of covalent modifications of hdl Apoproteins by endogenous oxidized phospholipids
Free Radical Biology and Medicine, 2017Co-Authors: Detao Gao, Eugene A PodrezAbstract:Abstract High density lipoprotein (HDL) is cardioprotective, unless it is pathologically modified under oxidative stress. Covalent modifications of lipid-free apoA-I, the most abundant Apoprotein in HDL, compromise its atheroprotective functions. HDL is enriched in oxidized phospholipids (oxPL) in vivo in oxidative stress. Furthermore, oxidized phospholipids can covalently modify HDL Apoproteins. We have now carried out a systematic analysis of modifications of HDL Apoproteins by endogenous oxPL. Human HDL or plasma were oxidized using a physiologically relevant MPO−H2O2−NO2− system or AIPH, or were exposed to synthetic oxPL. Protein adduction by oxPL was assessed using LC-MS/MS and MALDI-TOF MS. The pattern of HDL Apoprotein modification by oxPL was independent of the oxidation systems used. ApoA-I and apoA-II were the major modification targets. OxPL with a γ-hydroxy (or oxo)-alkenal were mostly responsible for modifications, and the Michael adduct was the most abundant adduct. Histidines and lysines in helices 5–8 of apoA-I were highly susceptible to oxPL modifications, while lysines in helices 1, 2, 4 and 10 were resistant to modification by oxPL. In plasma exposed to oxidation or synthetic oxPL, oxPL modification was highly selective, and four histidines (H155, H162, H193 and H199) in helices 6–8 of apoA-I were the main modification target. H710 and H3613 in apoB-100 of LDL and K190 of human serum albumin were also modified by oxPL but to a lesser extent. Comparison of oxPL with short chain aldehyde HNE using MALDI-TOF MS demonstrated high selectivity and efficiency of oxPL in the modification of HDL Apoproteins. These findings provide a novel insight into a potential mechanism of the loss of atheroprotective function of HDL in conditions of oxidative stress.
Detao Gao - One of the best experts on this subject based on the ideXlab platform.
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cross linking modifications of hdl Apoproteins by oxidized phospholipids structural characterization in vivo detection and functional implications
Journal of Biological Chemistry, 2020Co-Authors: Detao Gao, Mohammad Z Ashraf, Lifang Zhang, Niladri Kar, Tatiana V Byzova, Eugene A PodrezAbstract:Apolipoprotein A-I (apoA-I) is cross-linked and dysfunctional in human atheroma. Although multiple mechanisms of apoA-I cross-linking have been demonstrated in vitro, the in vivo mechanisms of cross-linking are not well-established. We have recently demonstrated the highly selective and efficient modification of high-density lipoprotein (HDL) Apoproteins by endogenous oxidized phospholipids (oxPLs), including γ-ketoalkenal phospholipids. In the current study, we report that γ-ketoalkenal phospholipids effectively cross-link Apoproteins in HDL. We further demonstrate that cross-linking impairs the cholesterol efflux mediated by apoA-I or HDL3 in vitro and in vivo Using LC-MS/MS analysis, we analyzed the pattern of Apoprotein cross-linking in isolated human HDL either by synthetic γ-ketoalkenal phospholipids or by oxPLs generated during HDL oxidation in plasma by the physiologically relevant MPO-H2O2-NO2- system. We found that five histidine residues in helices 5-8 of apoA-I are preferably cross-linked by oxPLs, forming stable pyrrole adducts with lysine residues in the helices 3-4 of another apoA-I or in the central domain of apoA-II. We also identified cross-links of apoA-I and apoA-II with two minor HDL Apoproteins, apoA-IV and apoE. We detected a similar pattern of Apoprotein cross-linking in oxidized murine HDL. We further detected oxPL cross-link adducts of HDL Apoproteins in plasma and aorta of hyperlipidemic LDLR-/- mice, including cross-link adducts of apoA-I His-165-apoA-I Lys-93, apoA-I His-154-apoA-I Lys-105, apoA-I His-154-apoA-IV Lys-149, and apoA-II Lys-30-apoE His-227. These findings suggest an important mechanism that contributes to the loss of HDL's atheroprotective function in vivo.
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characterization of covalent modifications of hdl Apoproteins by endogenous oxidized phospholipids
Free Radical Biology and Medicine, 2017Co-Authors: Detao Gao, Eugene A PodrezAbstract:Abstract High density lipoprotein (HDL) is cardioprotective, unless it is pathologically modified under oxidative stress. Covalent modifications of lipid-free apoA-I, the most abundant Apoprotein in HDL, compromise its atheroprotective functions. HDL is enriched in oxidized phospholipids (oxPL) in vivo in oxidative stress. Furthermore, oxidized phospholipids can covalently modify HDL Apoproteins. We have now carried out a systematic analysis of modifications of HDL Apoproteins by endogenous oxPL. Human HDL or plasma were oxidized using a physiologically relevant MPO−H2O2−NO2− system or AIPH, or were exposed to synthetic oxPL. Protein adduction by oxPL was assessed using LC-MS/MS and MALDI-TOF MS. The pattern of HDL Apoprotein modification by oxPL was independent of the oxidation systems used. ApoA-I and apoA-II were the major modification targets. OxPL with a γ-hydroxy (or oxo)-alkenal were mostly responsible for modifications, and the Michael adduct was the most abundant adduct. Histidines and lysines in helices 5–8 of apoA-I were highly susceptible to oxPL modifications, while lysines in helices 1, 2, 4 and 10 were resistant to modification by oxPL. In plasma exposed to oxidation or synthetic oxPL, oxPL modification was highly selective, and four histidines (H155, H162, H193 and H199) in helices 6–8 of apoA-I were the main modification target. H710 and H3613 in apoB-100 of LDL and K190 of human serum albumin were also modified by oxPL but to a lesser extent. Comparison of oxPL with short chain aldehyde HNE using MALDI-TOF MS demonstrated high selectivity and efficiency of oxPL in the modification of HDL Apoproteins. These findings provide a novel insight into a potential mechanism of the loss of atheroprotective function of HDL in conditions of oxidative stress.
Bas J Blaauboer - One of the best experts on this subject based on the ideXlab platform.
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comparison of cytochrome p450 isoenzyme profiles in rat liver and hepatocyte cultures the effects of model inducers on Apoproteins and biotransformation activities
Biochemical Pharmacology, 1991Co-Authors: Heleen M Wortelboer, C A De Kruif, A A J Van Iersel, H E Falke, Jan Noordhoek, Bas J BlaauboerAbstract:Abstract The metabolic profile of seven subfamilies of cytochrome P450 (P450IA, IIA, IIB, IIC, IIE, IIIA, IVA) was studied in rat liver (in vivo) and in primary hepatocyte cultures (in vitro) after treatment with various inducers. The dealkylation of 7-ethoxyresorufin (EROD) and 7-pentoxyresorufin (PROD), aniline 4-hydroxylation and the regio- and stereoselective hydroxylation of testosterone were measured to characterize the isoenzyme pattern in intact hepatocytes and in liver microsomes. Occurrence of isoenzyme Apoproteins was determined using Western blotting. Primary cultures of rat hepatocytes retain the capacity to respond to inducers of isoenzymes belonging to six different subfamilies (P450IA, IIA, IIB, IIC, IIIA and IVA). Treatment of cells with β-naphthoflavone revealed a P450-activity profile similar to in vivo, namely a highly induced EROD (P450IA1), a small enhancement of testosterone 7α-hydroxylation (P450IIA) and a marked reduction in 2α- and 16α-hydroxylation (P450IIC11). Exposure of cultured cells to phenobarbital resulted in a higher testosterone 16β-hydroxylation (reflecting P450IIB), though to a lesser extent than in vivo. The induction of P450IIIA due to both phenobarbital and dexamethasone, as mirrored by 6β- and 15β-hydroxylation of testosterone, was the same in cultured hepatocytes and in vivo. Treatment of cells with clofibric acid resulted in an induction profile similar to the one observed in liver microsomes from clofibrate-treated rats: the Apoprotein P450IVA as well as the Apoprotein P450IIB1/2 and its associated activities (PROD and testosterone 16β-hydroxylation) were induced. Isoniazid, a known in vivo inducer of P450IIE1 and aniline 4-hydroxylation, did not change any of the determined P450-dependent activities in vitro.
Hanitra Rabesona - One of the best experts on this subject based on the ideXlab platform.
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chemical and structural characterisation of low density lipoproteins purified from hen egg yolk
Food Chemistry, 2003Co-Authors: Marc Anton, Valérie Beaumal, Virginie Martinet, Michele Dalgalarrondo, Elisabeth Davidbriand, Hanitra RabesonaAbstract:Abstract Low-density lipoproteins (LDL) are considered to be the main contributors to the exceptional emulsifying activity of hen egg yolk. However, the lack of understanding of the molecular basis for LDL functionality is a significant obstacle for good control of yolk emulsions. Consequently, we have attempted to link the structure and the characteristics of LDL with their emulsifying properties. After purification of LDL, we have determined their protein and lipid compositions, their ultrastructure, and then extracted their Apoproteins for physicochemical characterisation. LDL are composed of about 12% of proteins and 87% of lipids and present a spherical shape with a mean diameter of about 35 nm. LDL solubility is high, whatever the medium conditions, because of their low density. LDL contain five major Apoproteins out of which the Apoprotein of 15 kDa is considered to be the most surface-active. After extraction, this Apoprotein showed a high proportion of amphipathic α-helix chains, explaining the high capacity of this Apoprotein to adsorb at the oil–water interface.
Chunhong Yang - One of the best experts on this subject based on the ideXlab platform.
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probing the pigment binding sites in lhcii with resonance raman spectroscopy the effect of mutations at s123
Biochimica et Biophysica Acta, 2016Co-Authors: Elizabeth Kish, Ke Wang, Manuel J Llansolaportoles, Cristian Ilioaia, Andrew A Pascal, Bruno Robert, Chunhong YangAbstract:Resonance Raman spectroscopy was used to evaluate the structure of light-harvesting chlorophyll (Chl) a/b complexes of photosystem II (LHCII), reconstituted from wild-type (WT) and mutant Apoproteins over-expressed in Escherichia coli. The point mutations involved residue S123, exchanged for either P (S123P) or G (S123G). In all reconstituted proteins, lutein 2 displayed a distorted conformation, as it does in purified LHCII trimers. Reconstituted WT and S123G also exhibited a conformation of bound neoxanthin (Nx) molecules identical to the native protein, while the S123P mutation was found to induce a change in Nx conformation. This structural change of neoxanthin is accompanied by a blue shift of the absorption of this carotenoid molecule. The interactions assumed by (and thus the structure of the binding sites of) the bound Chls b were found identical in all the reconstituted proteins, and only marginally perturbed as compared to purified LHCII. The interactions assumed by bound Chls a were also identical in purified LHCII and the reconstituted WT. However, the keto carbonyl group of one Chl a, originally free-from-interactions in WT LHCII, becomes involved in a strong H-bond with its environment in LHCII reconstituted from the S123P Apoprotein. As the absorption in the Qy region of this protein is identical to that of the LHCII reconstituted from the WT Apoprotein, we conclude that the interaction state of the keto carbonyl of Chl a does not play a significant role in tuning the binding site energy of these molecules.