Federal Institute for Risk Assessment, Department of Food Safety, Berlin, Germany.
Federal Institute for Risk Assessment, Department of Safety in the Food Chain, Berlin, Germany.
Toxicol Lett. 2014 Mar 3;225(2):311-7. doi: 10.1016/j.toxlet.2013.12.019. Epub 2013 Dec 25.
The consumption of okadaic acid (OA) contaminated shellfish can induce acute toxic symptoms in humans such as diarrhea, nausea, vomiting and abdominal pain; carcinogenic and embryotoxic effects have also been described. Toxicokinetic studies with mice have shown that high cytotoxic doses of OA can pass the gastrointestinal barrier presumably by paracellular passage. However, in vitro studies using human intestinal Caco-2 cell monolayers to represent the intestinal barrier have shown that at low-dose exposure OA is transported against a concentration gradient suggesting an active efflux mechanism. Since P-glycoprotein (P-gp) transports a wide variety of substrates, we investigated its possible influence on the observed elimination of OA. We used two different cellular transwell models: (i) Caco-2 cell monolayer endogenously expressing human P-gp and simulating the intestinal barrier and (ii) MDCK-II cell monolayer stably over-expressing P-gp. Our study demonstrates clearly that OA at non-cytotoxic concentrations passes the monolayer barrier only to a low degree, and that it is actively eliminated by P-gp over the apical membrane. Therefore, our in vitro data indicate that humans appear to have efficient defense mechanisms to protect themselves against low-dose contaminated shellfish by exhibiting a low bioavailability as a result of active elimination of OA by P-gp.
贝类受麻痹性贝毒（OA）污染后被人类食用，可能导致急性中毒症状，如腹泻、恶心、呕吐和腹痛；还描述了其致癌和胚胎毒性作用。用小鼠进行的毒代动力学研究表明，高细胞毒性剂量的 OA 可以通过细胞旁途径穿过胃肠道屏障。然而，使用代表肠道屏障的人肠道 Caco-2 细胞单层进行的体外研究表明，在低剂量暴露下，OA 逆浓度梯度转运，提示存在主动外排机制。由于 P-糖蛋白（P-gp）转运多种底物，我们研究了其对 OA 观察到的消除的可能影响。我们使用了两种不同的细胞 Transwell 模型：（i）内源性表达人 P-gp 并模拟肠道屏障的 Caco-2 细胞单层，和（ii）稳定过表达 P-gp 的 MDCK-II 细胞单层。我们的研究清楚地表明，OA 在非细胞毒性浓度下仅以低程度穿过单层屏障，并且通过 P-gp 从顶端膜主动消除 OA。因此，我们的体外数据表明，人类似乎具有有效的防御机制，通过 P-gp 主动消除 OA，使 OA 的生物利用度降低，从而免受低剂量污染贝类的侵害。
