Suppression of the in vitro humoral immune response of mouse splenocytes by 7,12-dimethylbenz[a]anthracene metabolites and inhibition of immunosuppression by alpha-naphthoflavone.
Suppression of the in vitro humoral immune response of mouse splenocytes by 7,12-dimethylbenz[a]anthracene metabolites and inhibition of immunosuppression by alpha-naphthoflavone.
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DOI：
10.1016/0041-008x(91)90287-o
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发表时间：
1991-08
影响因子：
3.8
通讯作者：
Gregory S. Ladics;Thomas T. Kawabata;K. White
中科院分区：
文献类型：
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作者：
Gregory S. Ladics;Thomas T. Kawabata;K. White
许多研究人员已经证明，暴露于7，12-二甲基苯并[a]蒽（DMBA）会抑制小鼠和培养的脾细胞的体液和细胞介导的免疫应答。然而，这种DMBA诱导的免疫抑制的机制还没有得到很好的表征。多环芳烃必须通过细胞色素P450依赖的单加氧酶系统转化为活性代谢物才能发挥其致癌和致突变作用。因此，我们假设，免疫抑制后看到暴露于DMBA也可能介导的反应性代谢产物。本研究的目的是确定DMBA代谢产物是否可以抑制体外对绵羊红细胞的T依赖性体液免疫应答。在体外空斑形成细胞（PFC）反应中，以10− 9至10− 5 m的浓度评价化合物。还评价了DMBA和苯并[a]芘（B[a]P）抑制体外PFC反应的能力。向脾细胞培养物中添加这些多环芳烃中的任何一种都会对PFC反应产生浓度依赖性抑制，其中发现B[a]P的效力是DMBA的17.5倍。这些结果与体内发现的结果形成鲜明对比，体内发现DMBA已被证明在抑制体液免疫方面比B[a]P更有效。DMBA的3，4-二醇代谢产物对体外PFC反应产生浓度依赖性抑制（10− 8至10− 5 m），并且被发现比母体化合物DMBA强65倍。相反，DMBA的5，6-二醇代谢产物对PFC反应或细胞活力没有影响。发现3-OH-DMBA和7-羟甲基-12-甲基-苯并[a]蒽（7-OHMe-12-Me-BA）代谢物在10− 6 m浓度下具有免疫抑制作用。此外，7-OHMe-12-Me-BA的抑制作用在低至10− 8 m的浓度下也被观察到。7-Me-12-OHMe-BA和二-OHMe-BA代谢产物的免疫抑制作用仅在高浓度（10− 5 m）下观察到。利用细胞色素P450抑制剂α-萘酚酮（ANF）来确定细胞色素P450介导的代谢是否参与DMBA诱导的体外PFC反应抑制。ANF（10− 5个月）逆转了DMBA诱导的10− 5个月的免疫抑制，并减弱了3 × 10− 5和10− 4个月的免疫抑制。这些研究的结果表明，DMBA的几种代谢产物，可以产生的细胞色素P450依赖性单加氧酶系统在体外PFC反应测定免疫抑制。此外，细胞色素P450抑制剂ANF能够逆转DMBA诱导的免疫抑制。然而，由于体外DMBA诱导和B[a] P诱导的体液免疫抑制的程度与体内观察到的不相关，因此脾脏内产生的DMBA代谢物可能不负责或可能仅部分有助于在整个动物中观察到的免疫抑制。
Exposure to 7,12-dimethylbenz[a]anthracene (DMBA) has been demonstrated by numerous investigators to result in suppression of both humoral and cell-mediated immune responses of mice and cultured splenocytes. The mechanism(s) of this DMBA-induced immunosuppression, however, is not well characterized. PAHs must be converted to reactive metabolites via cytochrome P450-dependent monooxygenase systems to exert their carcinogenic and mutagenic effects. Thus, we have hypothesized that immunosuppression seen upon exposure to DMBA may also be mediated by its reactive metabolites. The objective of this study was to determine if DMBA metabolites can suppress the in vitro, T-dependent humoral immune response to sheep red blood cells. Compounds were evaluated in the in vitro plaque-forming cell (PFC) response at concentrations of 10−9to 10−5m. DMBA and benzo[a]pyrene (B[a]P) were also evaluated for their ability to suppress the in vitro PFC response. Addition of either of these PAHs to splenocyte cultures produced a concentration-dependent suppression of the PFC response, in which B[a]P was found to be 17.5-fold more potent that DMBA. These results are in contrast to those found in vivo, where DMBA has been shown to be more potent than B[a]P at suppressing humoral immunity. The 3,4-diol metabolite of DMBA produced a concentration-dependent suppression (10−8to 10−5m) of the in vitro PFC response and was found to be 65-fold more potent than the parent compound DMBA. In contrast, the 5,6-diol metabolite of DMBA had no effect on the PFC response or cell viability. Both the 3-OH-DMBA and 7-hydroxymethyl-12-methyl-benz[a]anthracene (7-OHMe-12-Me-BA) metabolites were found to be immunosuppressive at concentrations of 10−6m. Furthermore, suppression by 7-OHMe-12-Me-BA was observed at concentrations as low as 10−8m. Immunosuppression by the 7-Me-12-OHMe-BA and the di-OHMe-BA metabolites was only observed at high (10−5m) concentrations. The cytochrome P450 inhibitor, α-naphthoflavone (ANF), was utilized to determine if cytochrome P450-mediated metabolism is involved in DMBA-induced suppression of the in vitro PFC response. ANF (10−5m) reversed the DMBA-induced immunosuppression seen at 10−5m and attenuated the immunosuppression at 3 × 10−5and 10−4m. The results of these studies demonstrate that several metabolites of DMBA which can be generated by the cytochrome P450-dependent monooxygenase systems are immunosuppressive in the in vitro PFC response assay. Furthermore, the cytochrome P450 inhibitor, ANF, was able to reverse DMBA-induced immunosuppression. However, since the degree of DMBA-induced and B[a]P-induced suppression of humoral immunity in vitro does not correlate with that observed in vivo, DMBA metabolites generated within the spleen may not be responsible for or may only partially contribute to the immunosuppression observed in the whole animal.