摘要:

A redox imbalance caused by an over-production of prooxidants or a decrease in antioxidants seems to play a role in the programmed cell death that occurs in various developmental programs. Such a physiological function for oxidative stress is particularly applicable to the immune system, wherein individual lymphocytes undergo continuous scrutiny to determine if they should be preserved or programmed to die. Following activation, lymphocytes produced increased levels of reactive oxygen species (ROS) which may serve as intracellular signaling molecules. The ultimate outcome of this increased ROS formation, i.e., lymphocyte proliferation versus programmed cell death, may be dictated by macrophage-derived costimulatory molecules that bolster or diminish lymphocyte antioxidant defenses. HIV-1-infected individuals display multiple symptoms of redox imbalance consistent with their being in oxidative stress, and lymphocytes from such individuals are more prone to undergo apoptosisin vitro. It is suggested that oxidative stress is a physiological mediator of programmed cell death in lymphoid cells, and that HIV disease represents an extreme case of what can happen when regulatory safeguards are compromised.

ISSN:1071-5762    

DOI:10.3109/10715769509147548

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The extent to which cells can oxidize LDL may be underestimated because of the use of standard and arbitrary 24 hourin vitroincubations of cells with LDL. Such incubations have resulted in inconsistent results regarding the ability of cell-mediated LDL oxidation to generate relatively advanced oxidation products such as 7-ketocholesterol (7-KC). We studied prolonged oxidation of low density lipoprotein (LDL) by mouse peritoneal macrophages using HPLC measurement of cholesterol, cholesteryl esters and their oxidation products 7-KC and cholesteryl linoleate hydroperoxide (CL-OOH). Cell-mediated oxidation in Ham's F10 consistently followed the successive stages previously described during 24 hour-10μM copper-mediated LDL oxidation, always generating 7-KC if allowed to proceed for sufficient time. The degree of inhibition of LDL oxidation achieved by metal chelators EDTA and DTPA at more advanced stages of cell-mediated LDL oxidation was not predictable from the published effects of such chelators upon early stages of metal-mediated and cell-mediated LDL oxidation. EDTA and DTPA only incompletely prevented the consumption of cholesteryl esters and the loss of preformed CL-OOH when added after cell-mediated LDL oxidation was established, while effectively concurrently inhibiting the generation of 7-KC. These data indicate that progressive cell-mediated peroxidation of LDL cholesteryl esters and decomposition of CL-OOH may be less dependent upon a continuing supply of redox active metals than is the generation of 7-KC. In addition, they confirm the plausibility of prolonged cell-mediated oxidation of LDL as a source of oxysterols found in human atherosclerotic plaque, and imply that active redox cycling of metals is particularly important for their generationin vivo.

ISSN:1071-5762    

DOI:10.3109/10715769509147549

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

The antioxidative activities of hamamelitannin (2′, 5-di-O-galloyl-hamamelose), gallic acid anddl-α-tocopherol against lipid peroxyl radicals were evaluated in chemical and biological systems. The peroxyl radical scavenging activity was evaluated by electron spin resonance (ESR) method in which both spin-trapping and direct reaction methods were used. In the spin-trapping method, as evaluated by 50%inhibition concentration (IC50) of peroxyl radicals generated in a t-butylhydroperoxide-methemoglobin system, hamamelitannin (IC50= 95.3±2.7μM) showed the highest activity, followed by gallic acid (IC50= 152.8±14.6μM) anddl-α-tocopherol (IC50= 221.5±4.6μM) as a positive control. When estimating by the direct method, IC50values of hamamelitannin, gallic acid anddl-α-tocopherol were 93.5±2.1μM, 141.6±2.0μM and 1590.0±330.0μM, respectively.On peroxidation of lipid bilayers induced by 2, 2′-azobis-(2-amidinopropane)dihydrochloride(AAPH) in terms of inhibition period (tinh), hamamelitannin showed the longest tinh time (1107.0±38.18 sec), followed by those ofdl-α-tocopherol (877.5±31.8 sec) and gallic acid (771.0±4.2 sec). The kinetic chain length, defined as the propagation numbers of a lipid peroxyl radical, and calculated from the ratio (Rp/Ri) of the rate of lipid peroxidation to that of inhibition bydl-α-tocopherol, hamamelitannin and gallic acid were 27.23, 7.86 and 7.09, respectively. The effects of hamamelitannin, gallic acid anddl-α-tocopherol were evaluated on murine fibroblasts exposed to t-butylhydroperoxide (BHP) in terms of the cell survivals. In the protection, hamamelitannin induced the highest survival of 27.6±0.6 % at 50μM, while both gallic acid and dl-α-tocopherol were less active at the same concentrations. On the basis of the results, hamamelitannin was concluded to have a high protective activity on cell damage induced by peroxides.

ISSN:1071-5762    

DOI:10.3109/10715769509147550

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

Alpha-tocopherol but not 2-carboxy-2,5,7,8-tetramethyl-6-chromanol (trolox or CTMC) and 2,2,5,7,8 pentamethyl-6-hydroxy chromane (PMC), derivatives ofα-tocopherol, inhibited the superoxide (O2−) generation of rat peritoneal neutrophils (RPMN) induced by phorbol 12-myristate 13-acetate (PMA). ID50for neutrophils obtained from the peritoneal cavity of rat and guinea pig was about 1μM. This concentration, however, was much lower than that for the inhibition of PMA-activated phospholipid-dependent protein kinase (PKC) (ID50= 30μM). Theα-tocopherol sensitive O2−generation was also observed in neutrophils induced by dioctanoylglycerol (diC8) and calcium ionophore A23187 but not by formylmethionyl-leucyl-phenylalanine (FMLP), opsonized zymosan (OZ) and sodium dodecyl sulfate (SDS). The pattern of inhibition byα-tocopherol was quite similar to that of staurosporine, a specific inhibitor of PKC. Theα-tocopherol content of RPMN was 12 ng/106cells and a linear increase to 200 ng/106cells by addition ofα-tocopherol to the cell suspension corresponded with an increased inhibition of O2−generation. These results indicate that both the chemical structure and the content ofα-tocopherol might be important factors in O2−generation by neutrophils.

ISSN:1071-5762    

DOI:10.3109/10715769509147551

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

摘要:

High field (400 and 600 MHz) proton NMR spectroscopy has been employed to investigate the thermally-induced autoxidation of glycerol-bound polyunsaturated fatty acids present in intact culinary frying oils and fats. Heating of these materials at 180°C for periods of 30, 60 and 90 min. generated a variety of peroxidation products, notably aldehydes (alkanals, trans-2-alkenals and alka-2, 4-dienals) and their conjugated hydroperoxydiene precursors. Since such aldehydes appear to be absorbed into the systemic circulation from the gut in vivo, the toxicological significance of their production during standard frying practices is discussed.

ISSN:1071-5762    

DOI:10.3109/10715769509147552

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor

ISSN:1071-5762    

DOI:10.3109/10715769509147553

出版商:Taylor&Francis    

年代:1995

数据来源: Taylor