Phosphatidylcholine hydroperoxide levels in human plasma are lower than previously reported

Branched-chain amino acids and l-carnitine attenuate lipotoxic hepatocellular damage in rat cirrhotic liver

Branched-chain amino acids (BCAA) reverse malnutrition and l-carnitine leads to the reduction of hyperammonemia and muscle cramps in cirrhotic patients. BCAA and l-carnitine are involved in glucose and fatty acid metabolism, however their mechanistic activity in cirrhotic liver is not fully understood. We aim to define the molecular mechanism(s) and combined effects of BCAA and l-carnitine using a cirrhotic rat model. Rats were administered carbon tetrachloride for 10 weeks to induce cirrhosis. During the last 6 weeks of administration, cirrhotic rats received BCAA, l-carnitine or a combination of BCAA and l-carnitine daily via gavage. We found that BCAA and l-carnitine treatments significantly improved hepatocellular function associated with reduced triglyceride level, lipid deposition and adipophilin expression, in cirrhotic liver. Lipidomic analysis revealed dynamic changes in hepatic lipid composition by BCAA and l-carnitine administrations. BCAA and l-carnitine globally increased molecular species of phosphatidylcholine. Liver triacylglycerol and phosphatidylcholine hydroperoxides were significantly decreased by BCAA and l-carnitine. Furthermore, serum and liver ATP levels were significantly increased in all treatments, which were attributed to the elevation of mature cardiolipins and mitochondrial component gene expressions. Finally, BCAA and l-carnitine dramatically reduced hepatocellular death. In conclusion, BCAA and l-carnitine treatments attenuate hepatocellular damage through the reduction of lipid peroxides and the overall maintenance of mitochondrial integrity within the cirrhotic liver. These effectiveness of BCAA and l-carnitine support the therapeutic strategies in human chronic liver diseases.

Phosphatidylcholine hydroperoxide promotes VEGF-induced angiogenesis in endothelial cells and rat aorta ring cultures

BACKGROUND

Phosphatidylcholine hydroperoxide (PCOOH) is a primary oxidation product of PC, and is markedly accumulated in blood plasma and arterial walls in atherosclerotic animals and humans. The role of PCOOH in the induction of angiogenesis is unknown.

METHODS

In this study, we investigated whether PCOOH stimulated angiogenic responses (e.g., vascular endothelial growth factor (VEGF)-induced cell proliferation, migration, and tube formation, and angiogenesis-related gene/protein expression) in human umbilical vein endothelial cells (HUVEC) and in an ex vivo rat aorta model.

RESULTS

VEGF induced proliferation, migration, and tube formation of HUVEC, and these angiogenic responses were all enhanced by PCOOH but not by native (nonoxidized) PC. The angiogenic effects of PCOOH are considered to be mediated via generation of reactive oxygen species and activation of both PI3K/AKT and MAPK pathways. The angiogenic activities of PCOOH were also confirmed by the rat aortic ring assay.

CONCLUSIONS

These results indicate that PCOOH can elicit several angiogenic responses.

GENERAL SIGNIFICANCE

The present study implies an important role of PCOOH in atherosclerosis progression and plaque instability.

Combination of TLC Blotting and Gas Chromatography–Mass Spectrometry for Analysis of Peroxidized Cholesterol

We have established a sensitive and convenient method for analysis of cholesterol hydroperoxides (Chol-OOHs) as trimethylsilyloxyl derivatives using diphenylpyrenylphosphine (DPPP)-thin-layer chromatography (TLC) blotting and gas chromatography-electron ionization-mass spectrometry/selected-ion monitoring (GC-EI-MS/SIM). Chol-OOH standards were prepared by photosensitized oxidation and azo radical-induced peroxidation of cholesterol. Trimethylsilyloxyl derivatives of cholesterol 5alpha-hydroperoxide (Chol 5alpha-OOH), cholesterol 7alpha-hydroperoxide (Chol 7alpha-OOH), and cholesterol 7beta-hydroperoxide (Chol 7beta-OOH) could be separated from one another in the SIM chromatogram using a fragment ion with elimination of trimethylsilanol from the molecular ion. This method was used to characterize peroxidized cholesterol from azo radical-exposed human low-density lipoprotein and UVA-irradiated human keratinocytes in the presence of hematoporphyrin. Finally, we succeeded in the quantification of each Chol-OOH isomer present in hairless mouse skin with and without UVA irradiation by use of beta-sitosterol hydroperoxide as internal standard. The accumulation of Chol 5alpha-OOH with Chol 7alpha/betaOOH in the skin indicates that singlet molecular oxygen ((1)O(2)) participated in the peroxidation of skin cholesterol, because Chol 5alpha-OOH is known to be a (1)O(2) specific cholesterol peroxidation product. We concluded that the combination of DPPP-TLC blotting and GC-EI-MS/SIM is useful for quantifying peroxidized cholesterol in biological samples and confirming the participation of (1)O(2) in oxidative stress.

Detection of phosphatidylcholine oxidation products in rat heart using quadrupole time-of-flight mass spectrometry

An improved technique for the analysis of phosphatidylcholine (PC) and lyso-phosphatidylcholine (lyso-PC) oxidation products was developed using quadrupole time of flight (Q-TOF) mass spectrometry with electrospray ionization. We separated these products using an HPLC C(8) column with a gradient of methanol and 10mM aqueous ammonium acetate. Monohydroxides, oxo derivatives, and trihydroxides of palmitoyl-linoleoyl (C16:0/C18:2) PC, stearoyl-linoleoyl (C18:0/C18:2) PC, and oleoyl-linoleoyl (C18:1/C18:2) PC were detected mainly as MH(+) and [M+Na](+) ions in the heart of the intact rat. Using standard synthetic PC-OH (C16:0/C18:2-OH), the lipid extract component was identified as (C16:0/C18:2-OH) PC based on the product ions of ESI-MS-MS and, the PC-OH concentration was quantitated. Four oxidatively modified 1-lyso-phosphatidylcholines (lyso-PCs) were also detected. This is the first report showing the presence of monohydroxides, oxo derivatives, and trihydroxides of (C16:0/C18:2)PC, (C18:0/C18:2)PC, and (C18:1/C18:2) PC in the rat heart.

Triacylglycerol oxidation in pig lipoproteins after a diet rich in oxidized sunflower seed oil

The effects of two sunflower seed oil diets differing in oxidation levels (PV in oils 1 and 190 mequiv O2/kg) on lipoprotein TAG and total lipid oxidation were investigated in growing pigs. For 2 wk, two groups of 10 pigs were fed either of the diets, after which blood samples were collected. A method based on RP-HPLC and electrospray ionization-MS was used for the analysis of oxidized TAG molecules in chylomicrons and VLDL. The baseline diene conjugation method was used for the estimation of in vivo levels of lipoprotein lipid oxidation. TAG molecules with a hydroxy, an epoxy, or a keto group attached to a FA, as well as TAG core aldehydes were detected in the samples. Typically, lipoprotein TAG and total lipids were more oxidized in the pigs fed on the oxidized oil compared with those fed on nonoxidized oil. Oxidation of dietary fat was thus reflected in the lipoprotein oxidation, which confirmed our earlier findings.