Hoepelman I M, Bezemer W A, Vandenbroucke-Grauls C M, Marx J J, Verhoef J
Department of Internal Medicine, University Hospital Utrecht, The Netherlands.
Infect Immun. 1990 Jan;58(1):26-31. doi: 10.1128/iai.58.1.26-31.1990.
It has been shown that increasing bacterial iron concentration enhances killing by hydrogen peroxide (H2O2) but not by polymorphonuclear granulocytes (PMN). It is possible that owing to the multiple bactericidal mechanisms of the PMN, differences in the killing rate of iron-loaded bacteria and control bacteria are obscured. We decided, therefore, to compare the killing of iron-loaded bacteria with that of control bacteria using human monocytes (MN), PMN, and PMN-derived cytoplasts. Incubation of Staphylococcus aureus with increasing concentrations of ferrous ammonium sulfate (0 to 1,000 microM) progressively increased the iron content in the bacteria (from 0.01 to 0.24 mumol of iron per 10(9) bacteria). Iron loading of the bacteria markedly increased their susceptibility to killing by H2O2. After 1 h of incubation with 1 mM H2O2, 95 +/- 2% of the iron-loaded bacteria were killed compared with 18 +/- 4% of the control bacteria (P less than 0.0001). Iron loading of bacteria did not alter their susceptibility to killing by human PMN. However, iron-loaded bacteria were more susceptible to killing by MN (after 12 min of incubation, 81 +/- 2 versus 74 +/- 2% killing; P less than 0.008) and to killing by PMN-derived cytoplasts (after 60 min of incubation, 52 +/- 8 versus 33 +/- 5%; P = 0.003) than the controls. Moreover, iron loading enhanced luminol-mediated chemiluminescence of MN, PMN, and PMN-derived cytoplasts. The hydroxyl radical scavenger thiourea inhibited H2O2-mediated killing of iron-loaded staphylococci as well as luminol-mediated chemiluminescence. These results suggest that alterations in intrinsic iron content increase killing of staphylococci by H2O2, MN, and PMN-derived cytoplasts by a free radical-mediated mechanism.
研究表明，增加细菌铁浓度可增强过氧化氢（H2O2）的杀菌作用，但对多形核粒细胞（PMN）的杀菌作用无影响。由于PMN具有多种杀菌机制，铁负载细菌与对照细菌的杀灭率差异可能被掩盖。因此，我们决定用人单核细胞（MN）、PMN和PMN衍生的胞质体比较铁负载细菌与对照细菌的杀灭情况。用不同浓度的硫酸亚铁铵（0至1000 microM）孵育金黄色葡萄球菌，可使细菌中的铁含量逐渐增加（从每10^9个细菌含0.01至0.24微摩尔铁）。细菌铁负载显著增加了它们对H2O2杀灭的敏感性。用1 mM H2O2孵育1小时后，95±2%的铁负载细菌被杀死，而对照细菌为18±4%（P＜0.0001）。细菌铁负载并未改变其对人PMN杀灭的敏感性。然而，与对照相比，铁负载细菌对MN的杀灭更敏感（孵育12分钟后，杀灭率分别为81±2%和74±2%；P＜0.008），对PMN衍生的胞质体的杀灭也更敏感（孵育60分钟后，杀灭率分别为52±8%和33±5%；P = 0.003）。此外，铁负载增强了MN、PMN和PMN衍生胞质体的鲁米诺介导的化学发光。羟基自由基清除剂硫脲可抑制H2O2介导的铁负载葡萄球菌的杀灭以及鲁米诺介导的化学发光。这些结果表明，内在铁含量的改变通过自由基介导的机制增加了H2O2、MN和PMN衍生胞质体对葡萄球菌的杀灭作用。
