Osaka K, Ritov V B, Bernardo J F, Branch R A, Kagan V E
Department of Environmental and Occupational Health, University of Pittsburgh, Pennsylvania 15238, USA.
Antimicrob Agents Chemother. 1997 Apr;41(4):743-7. doi: 10.1128/AAC.41.4.743.
The antifungal effects of amphotericin B are believed to be due to two possibly interrelated mechanisms: an increase in permeation by binding to sterols in cellular membranes and a prooxidant effect causing oxidative damage in target cells. However, the seven conjugated double bonds in amphotericin B raise the possibility that it could be highly susceptible to autoxidation, causing an antioxidant effect. In the present study, we investigated the prooxidant and antioxidant properties of amphotericin B in a model system in which oxidation of a reporter molecule, cis-parinaric acid, was induced by azo initiators of peroxyl radicals. Since interactions of amphotericin B with sterols are essential for its pharmacological and toxic actions, we also studied the effects of cholesterol on the prooxidant and antioxidant properties of amphotericin B. Amphotericin B caused a noncollisional quenching of a characteristic fluorescence of cholesteryl cis-parinarate integrated in liposomes, suggesting the formation of amphotericin B-cholesteryl cis-parinarate complex. This effect of amphotericin B was ablated by increasing concentrations of cholesterol. We found that amphotericin B inhibited oxidation of cis-parinaric acid complexed with human serum albumin [using a water-soluble azo initiator, 2,2'-azobis(2aminopropane)dihydrochloride] and in liposomes [using a lipid-soluble azo initiator, 2,2'-azobis(2,4-dimethylvaleronitrile)]. The inhibitory effect of amphotericin B on 2,2'-azobis(2,4-dimethylvaleronitrile)-induced peroxidation of cis-parinaric acid in liposomes was also diminished by cholesterol. The antioxidant effect of amphotericin B in this model system suggests that amphotericin B does not exert its pharmacological and toxicological responses through a prooxidant effect to cause damage in target cells.
两性霉素B的抗真菌作用被认为归因于两种可能相互关联的机制：通过与细胞膜中的固醇结合增加通透性，以及导致靶细胞氧化损伤的促氧化作用。然而，两性霉素B中的七个共轭双键增加了其可能对自氧化高度敏感从而产生抗氧化作用的可能性。在本研究中，我们在一个模型系统中研究了两性霉素B的促氧化和抗氧化特性，在该系统中，过氧自由基的偶氮引发剂诱导报告分子顺式-十八碳四烯酸的氧化。由于两性霉素B与固醇的相互作用对其药理和毒性作用至关重要，我们还研究了胆固醇对两性霉素B促氧化和抗氧化特性的影响。两性霉素B导致整合在脂质体中的胆固醇顺式-十八碳四烯酸的特征荧光发生非碰撞猝灭，表明形成了两性霉素B-胆固醇顺式-十八碳四烯酸复合物。两性霉素B的这种作用随着胆固醇浓度的增加而消失。我们发现两性霉素B抑制与人类血清白蛋白复合的顺式-十八碳四烯酸的氧化[使用水溶性偶氮引发剂2,2'-偶氮二(2-氨基丙烷)二盐酸盐]以及脂质体中顺式-十八碳四烯酸的氧化[使用脂溶性偶氮引发剂2,2'-偶氮二(2,4-二甲基戊腈)]。胆固醇也减弱了两性霉素B对2,2'-偶氮二(2,4-二甲基戊腈)诱导的脂质体中顺式-十八碳四烯酸过氧化的抑制作用。两性霉素B在该模型系统中的抗氧化作用表明，两性霉素B并非通过促氧化作用对靶细胞造成损伤来发挥其药理和毒理反应。
