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Query: UMLS:C0004153 (atherosclerosis)
 77,401 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Oxidative modification of human low-density lipoprotein (LDL) is thought to play an important role in the development of atherosclerosis. LDL oxidizability is believed to be strongly influenced by factors such as (a) content of preexisting lipid hydroperoxides (LOOHs) and (b) content of endogenous antioxidants such as alpha-tocopherol and beta-carotene. The purpose of this study was to examine the prooxidant role of preexisting LDL-LOOHs, using a recently developed method for ultrasensitive and selective LOOH analysis: high-performance liquid chromatography with mercury drop electrochemical detection (HPLC-EC). Exceedingly low detection limits for LDL-LOOHs have been achieved by HPLC-EC, e.g., approximately 100 fmol for cholesteryl ester hydroperoxide (CEOOH). This sensitivity has allowed us to monitor LDL-LOOHs at levels that are undetectable by most other methods. Fresh LDL prepared with the utmost care to prevent autoxidation was found to contain small, yet significant amounts of CEOOH, 6-12 pmol/mg protein. Our data suggest that these peroxides could not have arisen during LDL isolation or sample work-up for HPLC-EC. Incubation with GSH and phospholipid hydroperoxide glutathione peroxidase resulted in nearly complete reduction of the CEOOH. This LDL was found to be much more resistant to Cu(2+)-induced peroxidation than starting material, exhibiting a lag period that was at least six times greater. We have also determined that LDL becomes progressively more susceptible to Cu(2+)-induced lipid peroxidation (as evidenced by a shortened lag) when it is preloaded with increasing amounts of photochemically generated LOOHs. Taken together, these results provide strong support for the idea that preexisting LOOHs in LDL are important determinants of its overall oxidizability.
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PMID:Involvement of preexisting lipid hydroperoxides in Cu(2+)-stimulated oxidation of low-density lipoprotein. 798 64

Rabbit abdominal aortic smooth muscle cells (SMC) were stably transfected with the cDNA of porcine phospholipid hydroperoxide glutathione peroxidase (PHGPx) by means of a retroviral gene transfer technique, to create a model for studying cellular processes relevant to atherogenesis. The transfected cells (SMC/PHGPx) had approximately 4-fold higher PHGPx activity when cultured in the presence of selenite whereas the parental cells did not show any significant increase in PHGPx or total GPx activity upon selenium supplementation. In situ functionality of PHGPx was validated by inhibition of linoleic acid hydroperoxide-induced toxicity, dihydrorhodamine oxidation, NFkappaB activation and apoptosis. SMC grown in 1% FCS responded to oxidized LDL (oxLDL) with a marked proliferation, as measured by [3H]thymidine incorporation, irrespective of selenium supplementation. In SMC/PHGPx grown with or without selenite under control conditions or exposed to native LDL, thymidine incorporation was generally depressed. Also, oxLDL-induced proliferation was lower in SMC/PHGPx compared to untransfected SMC up to 24 h of incubation. After 40 h, however, selenite supplementation restored maximum proliferation response to oxLDL in SMC/PHGPx. The results suggest a proliferative effect of endogenous hydroperoxides in SMC. They further reveal that hydroperoxy lipids of oxLDL contribute to the induction of proliferation, but also suggest involvement of hydroxy lipids in the response to oxLDL.
Atherosclerosis 2000 Oct
PMID:Overexpression of PHGPx inhibits hydroperoxide-induced oxidation, NFkappaB activation and apoptosis and affects oxLDL-mediated proliferation of rabbit aortic smooth muscle cells. 1099 58

Phospholipid hydroperoxide glutathione peroxidase (GPx4) is the only antioxidant enzyme known to directly reduce phospholipid hydroperoxides within membranes and lipoproteins, acting in conjunction with alpha-tocopherol to inhibit lipid peroxidation. Peroxidation of lipids has been implicated in a number of pathophysiological processes, including inflammation and atherogenesis. We investigated the relative positive and negative effects of specific polyunsaturated fatty acids (PUFAs) and inflammatory cytokines on the activity and gene expression of the selenium-dependant redox enzyme GPx4. In human umbilical vein endothelial cells (HUVEC), GPx4 mRNA levels and activity were increased optimally by 114 nM selenium (as sodium selenite). Docosahexaenoic acid (DHA) and conjugated linoleic acid (CLA) further increased mRNA levels whereas arachidonic acid (ARA) had no effect; enzyme activity was decreased by DHA, was unaffected by CLA or was increased by ARA. GPx4 protein levels increased with selenium, ARA and DHA addition but not with CLA. Interleukin-1beta (IL-1beta) increased GPx4 mRNA, protein and activity whereas TNFalpha at 1 ng/ml increased activity while at 3 ng/ml it reduced activity and mRNA. Conversely, alpha-tocopherol reduced mRNA levels without affecting activity. These results indicate that lipids, cytokines and antioxidants modulate GPx4 in a complex manner that in the presence of adequate selenium, may favour protection against potentially proatherogenic processes.
Atherosclerosis 2003 Nov
PMID:Regulation of selenoprotein GPx4 expression and activity in human endothelial cells by fatty acids, cytokines and antioxidants. 1464 6

Cytokines or hydroperoxides upregulate cell adhesion molecules (CAM) in early stages of atherosclerosis. VCAM-1 expression was therefore investigated in rabbit aortic smooth muscle cells (SMC) stably transfected either with phospholipid hydroperoxide glutathione peroxidase (PHGPx; SMCPHGPx) as a hydroperoxide-reducing enzyme or with 15-lipoxygenase (15-LOX; SMCLOX) as a hydroperoxide-producing enzyme. Transfected cells showed up to 3-fold enhanced PHGPx and a marked LOX activity, respectively, that was absent in controls. Intracellular hydroperoxides were 6-fold higher in SMCLOX than in SMC or SMCPHGPx. Intracellular protein thiols were decreased by 50 and 90% in SMCPHGPx and SMCLOX, respectively. Glutathione mixed disulfides were tentatively increased from SMC via SMCPHGPx to SMCLOX, accordingly. Thiol reduction with tris(2-carboxyethyl)phosphine completely restored protein thiols in SMCPHGPx, whereas in SMCLOX only 60% of control values were recovered. Basal VCAM-1 mRNA levels were decreased by 50% in SMCPHGPx and 75% in SMCLOX. VCAM-1-inducibility was abrogated in SMCLOX but not in SMCPHGPx. Accordingly, NFkappaB-driven reporter gene activation by IL-1 was unaffected in SMCPHGPx but abolished in SMCLOX. The data confirm that PHGPx overexpression dampens CAM expression either by lowering stimulatory hydroperoxides or by using hydroperoxides for protein modification. But hydroperoxides, when constitutively overproduced as in SMCLOX, inhibit CAM expression and render cells refractory to IL-1 stimulation likely due to oxidation of protein thiols of the signaling system.
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PMID:Inhibition of basal and interleukin-1-induced VCAM-1 expression by phospholipid hydroperoxide glutathione peroxidase and 15-lipoxygenase in rabbit aortic smooth muscle cells. 1474 25