Ladics G S, Kawabata T T, Munson A E, White K L
Department of Pharmacology and Toxicology, Medical College of Virginia, Virginia Commonwealth University, Richmond 23298.
Toxicol Appl Pharmacol. 1992 Oct;116(2):258-66. doi: 10.1016/0041-008x(92)90305-c.
Recent studies have demonstrated that macrophages are the cell types capable of metabolizing benzo[a]pyrene (B(a)P) within the spleens of untreated mice. Since repeated exposure to B(a)P results in immunosuppression and B(a)P is known to induce cytochrome P450 levels, the first objective of this study was to investigate whether exposure of mice to B(a)P could increase the amounts of immunosuppressive B(a)P metabolites generated and/or alter the pattern of B(a)P metabolites formed by several different splenic cell types. Mice were dosed with a daily sc dose of 200 mg/kg B(a)P or vehicle for 4 days. Separation of splenocytes based on density by centrifugation through discontinuous Percoll gradients along with immunomagnetic negative selection or antibody-mediated complement lysis was used to obtain different splenic cell populations. Cells were incubated with [3H]B(a)P for 24 hr. High-pressure liquid chromatography was used to separate and quantitate B(a)P metabolites. Results indicate that splenic macrophages of B(a)P-treated mice produced significantly greater amounts of some metabolites compared to those of vehicle-treated mice. The three major metabolites produced were an unidentified peak of polar metabolites containing polyhydroxylated metabolites, B(a)P-9,10- and B(a)P-7,8-dihydrodiols. Other splenic cell types examined did not produce metabolite amounts significantly above (T-cells, PMNs, or the capsule) or just above (B-cells) background. The second objective was to investigate the splenic cell type(s) targeted by B(a)P resulting in suppression of humoral immunity. Separation-reconstitution studies along with in vitro sensitization techniques with several different antigens (sheep red blood cells (SRBC), dinitrophenyl-Ficoll (DNP-Ficoll), lipopolysaccharide (LPS)) were used to identify splenic target cells following exposure of mice to B(a)P (200 mg/kg/day, sc for 4 days). Findings indicate that in vitro plaque-forming cell (PFC) suppression was due to alterations in the adherent (macrophage) cell population. Exposure also suppressed the PFC response to the T-dependent antigen SRBC and the T-independent antigen DNP-Ficoll, but did not suppress the PFC response to the polyclonal antigen, LPS. These data suggest that B(a)P is targeting macrophages.
最近的研究表明，巨噬细胞是未处理小鼠脾脏内能够代谢苯并[a]芘（B(a)P）的细胞类型。由于反复接触B(a)P会导致免疫抑制，且已知B(a)P会诱导细胞色素P450水平，因此本研究的首要目标是调查小鼠接触B(a)P是否会增加免疫抑制性B(a)P代谢产物的生成量和/或改变几种不同脾细胞类型形成的B(a)P代谢产物模式。给小鼠每日皮下注射剂量为200 mg/kg的B(a)P或赋形剂，持续4天。通过不连续Percoll梯度离心法根据密度分离脾细胞，并结合免疫磁珠阴性选择或抗体介导的补体裂解来获得不同的脾细胞群体。将细胞与[3H]B(a)P孵育24小时。使用高压液相色谱法分离和定量B(a)P代谢产物。结果表明，与接受赋形剂处理的小鼠相比，接受B(a)P处理的小鼠的脾巨噬细胞产生的某些代谢产物量显著更高。产生的三种主要代谢产物是一个包含多羟基化代谢产物的极性代谢产物的未鉴定峰、B(a)P-9,10-二醇和B(a)P-7,8-二醇。所检测的其他脾细胞类型产生的代谢产物量未显著高于（T细胞、中性粒细胞或被膜）或仅略高于（B细胞）背景值。第二个目标是研究B(a)P靶向导致体液免疫抑制的脾细胞类型。采用分离-重组研究以及针对几种不同抗原（绵羊红细胞（SRBC）、二硝基苯基-菲可（DNP-菲可）、脂多糖（LPS））的体外致敏技术，以确定小鼠接触B(a)P（200 mg/kg/天，皮下注射4天）后的脾靶细胞。研究结果表明，体外空斑形成细胞（PFC）抑制是由于黏附（巨噬细胞）细胞群体的改变。接触还抑制了对T细胞依赖性抗原SRBC和T细胞非依赖性抗原DNP-菲可的PFC反应，但未抑制对多克隆抗原LPS的PFC反应。这些数据表明B(a)P靶向巨噬细胞。
