Oxidative modification of high-density lipoprotein 3 induced by human polymorphonuclear neutrophils - Protective effect of pentoxifylline

The function of high-density lipoproteins (HDLs) in reverse cholesterol tra nsport is impaired if HDLs are subjected to oxidative stress. Polymorphonuc lear neutrophils (PMNs), which have been detected in the earliest stages of atherosclerotic lesions, are one of the most likely sources of the reactiv e oxygen species that cause such stress. In this study, we investigated the effect of a PMN oxidative burst on HDL3. We also studied the impact on these events of pentoxifylline, a drug that regulates granulocyte function. HDL3 (370 nmol . mL(-1) cholesterol-HDL) was incubated with PMNs (2 x 10(6) . mL(-1)) in NaCl/P-i in the presence or absence of an iron chelate comple x (10 mu M Fe-nitrilotriacetic acid) at 37 degrees C for 60 min or 24 h. Ph orbol myristate acetate (PMA) or formyl-methionylleucyphenylalanine (fMetLe uPhe) was used to stimulate PMNs. In iron-free NaCl/P-i medium, PMA-stimula ted PMNs had a 40% lower HDL3 alpha-tocopherol content, whatever the incuba tion time. In NaCl/P-i medium containing iron, there was 80% less HDL3 alph a-tocopherol at 60 min, and HDL3 alpha-tocopherol had almost disappeared af ter 24 h. In this latter condition, the amount of thiobarbituric acid-react ive substances was significantly higher than the respective control HDL3 (P < 0.05) and oxidation of HDL3 by PMA stimulated PMNs was associated with c ross-linking of apoprotein AI, which was detected by SDS/PAGE. Similar resu lts were obtained with fMetLeuPhe-stimulated PMN except that HDL3 alpha-toc opherol was consumed much more slowly during the first 60 min. Pretreatment of PMNs with various concentrations of pentoxifylline (0.001-20 mM) led to the concentration-dependent inhibition of oxidative modification of HDL3 i nduced by stimulated PMNs. The addition of 20 mM pentoxifylline in the most extreme oxidative stress conditions resulted in 70% of HDL3 alpha-tocopher ol being maintained, with no formation of thiobarbituric acid-reactive subs tances and a lower level of apoprotein AI cross-linking. Thus HDL3 is susceptible to oxidative modifications induced by stimulated P MNs, in the presence of an exogenous source of iron. Pentoxifylline inhibit ed the oxidative modification of HDL3 by PMNs.