Schwarzer E, Ludwig P, Valente E, Arese P
Dipartimento di Genetica, Biologia e Chimica Medica, Università di Torino, Italy.
Parassitologia. 1999 Sep;41(1-3):199-202.
Several studies have shown that human and murine hemozoin-fed phagocytes are functionally impaired. Unpurified hemozoin contains unspecifically attached unsaturated fatty acids such as arachidonic and linolenic acids. The presence in unpurified hemozoin of large quantities of ferric heme with small amounts of free iron makes hemozoin a generator of oxidative radicals capable of forming lipoperoxides or other breakdown products from polyunsaturated fatty acids. Here we show that delipidized hemozoin had reduced toxicity to monocytes. Phorbol myristate acetate (PMA)-elicited burst was poorly affected by delipidized hemozoin (ca. 17% and 21% burst inhibition by delipidized hemozoin vs ca. 75% and 65% burst inhibition by native hemozoin at 20 min or 17 h post-phagocytosis, respectively). Analysis of the lipid fraction isolated from native hemozoin by HPLC and chiral-phase HPLC showed equimolar amounts of 15(R)- and 15(S)-HETE (HETE, 15-hydroxy-6,8,11,13-eicosatetraenoic acid), most likely by-products of non-enzymatic peroxidation of arachidonic acid. The biologically active isomer, 15(S)-HETE, the product of 15-lipoxygenase, is a powerful mediator of inflammation and the effector of a large number of bioactions. 15(R,S)-HETE was found in native hemozoin (0.24 millimole/mole hemozoin heme), in supernatants of hemozoin-fed monocytes (87 nMol) and in hemozoin-fed monocytes (9.6 microMol). Approximately 84% of 15-HETE attached to hemozoin was in the esterified form. A large preponderance of esterified over free 15-HETE was also noted in supernatants of hemozoin-fed monocytes and in hemozoin-fed monocytes. In the latter cells, remarkable levels of the substance were attained. A dose-dependent curve of inhibition of PMA-elicited oxidative burst was observed. Assuming homogenuous distribution of 15-HETE in hemozoin-fed monocytes, 15(S)-HETE concentrations measured in hemozoin-fed monocytes (8 muMol) would bring about ca. 85% inhibition of PMA-elicited burst. In conclusion, derivatives of lipoperoxidation of unsaturated fatty acids such as 4-hydroxynonenal, 15-HETE and others now under study, appear to be relevant causes of hemozoin toxicity.
多项研究表明，吞噬了人源和鼠源疟原虫血红素的吞噬细胞功能受损。未纯化的疟原虫血红素含有非特异性附着的不饱和脂肪酸，如花生四烯酸和亚麻酸。未纯化的疟原虫血红素中大量的三价铁血红素与少量的游离铁共存，使得疟原虫血红素成为氧化自由基的产生源，能够从多不饱和脂肪酸中形成脂过氧化物或其他分解产物。在此我们表明，脱脂的疟原虫血红素对单核细胞的毒性降低。佛波酯（PMA）诱导的呼吸爆发受脱脂疟原虫血红素的影响较小（吞噬后20分钟或17小时，脱脂疟原虫血红素对呼吸爆发的抑制率约为17%和21%，而天然疟原虫血红素的抑制率约为75%和65%）。通过高效液相色谱（HPLC）和手性相HPLC分析从天然疟原虫血红素中分离出的脂质部分，结果显示15（R）-和15（S）-羟基二十碳四烯酸（HETE）的量相等，很可能是花生四烯酸非酶促过氧化的副产物。具有生物活性的异构体15（S）-HETE是15-脂氧合酶的产物，是一种强大的炎症介质和大量生物作用的效应物。在天然疟原虫血红素（0.24毫摩尔/摩尔疟原虫血红素血红素）、吞噬疟原虫血红素的单核细胞上清液（87纳摩尔）和吞噬疟原虫血红素的单核细胞（9.6微摩尔）中均发现了15（R，S）-HETE。附着在疟原虫血红素上的15-HETE约84%为酯化形式。在吞噬疟原虫血红素的单核细胞上清液和吞噬疟原虫血红素的单核细胞中也发现酯化的15-HETE大大超过游离的15-HETE。在后者细胞中，该物质达到了显著水平。观察到了PMA诱导的氧化爆发抑制的剂量依赖性曲线。假设15-HETE在吞噬疟原虫血红素的单核细胞中均匀分布，则在吞噬疟原虫血红素的单核细胞中测得的15（S）-HETE浓度（8微摩尔）将导致约85%的PMA诱导的爆发受到抑制。总之，不饱和脂肪酸脂过氧化的衍生物，如4-羟基壬烯醛、15-HETE及其他正在研究的物质，似乎是疟原虫血红素毒性的相关原因。
