Department of Biology, Queens College, City University of New York, 65-30 Kissena Blvd, Queens NY 11367-1597, USA; The Graduate Center, City University of New York, 365 Fifth Avenue, New York, NY 10016, USA.
Department of Biology, Queens College, City University of New York, 65-30 Kissena Blvd, Queens NY 11367-1597, USA; The Graduate Center, City University of New York, 365 Fifth Avenue, New York, NY 10016, USA.
Aquat Toxicol. 2021 Apr;233:105794. doi: 10.1016/j.aquatox.2021.105794. Epub 2021 Feb 25.
Polychlorinated biphenyls (PCBs) and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) are environmental contaminants known to impact cardiac development, a key step in the embryonic development of most animals. To date, little is understood of the molecular mechanism driving the observed cardiac defects in exposed fishes. The literature shows PCB & TCDD derived cardiac defects are concurrent with, but not caused by, expression of cyp1A, due to activation of the aryl hydrocarbon receptor (AhR) gene activation pathway. However, in this study, detailed visualization of fish hearts exposed to PCBs and TCDD show that, in addition to a failure of cardiac looping in early heart development, the inner endocardial lining of the heart fails to maintain proper cell adhesion and tissue integrity. The resulting gap between the endocardium and myocardium in both zebrafish and Atlantic sturgeon suggested functional faults in endothelial adherens junction formation. Thus, we explored the molecular mechanism triggering cardiac defects using immunohistochemistry to identify the location and phosphorylation state of key regulatory and adhesion molecules. We hypothesized that PCB and TCDD activates AhR, phosphorylating Src, which then phosphorylates the endothelial adherens junction protein, VEcadherin. When phosphorylated, VEcadherin dimers, found in the endocardium and vasculature, separate, reducing tissue integrity. In zebrafish, treatment with PCB and TCDD contaminants leads to higher phosphorylation of VEcadherin in cardiac tissue suggesting that these cells have reduced connectivity. Small molecule inhibition of Src phosphorylation prevents contaminant stimulated phosphorylation of VEcadherin and rescues both cardiac function and gross morphology. Atlantic sturgeon hearts show parallels to contaminant exposed zebrafish cardiac phenotype at the tissue level. These data suggest that the mechanism for PCB and TCDD action in the heart is, in part, distinct from the canonical mechanism described in the literature and that cardiac defects are impacted by this nongenomic mechanism.
多氯联苯 (PCBs) 和 2,3,7,8-四氯二苯并对二恶英 (TCDD) 是已知会影响心脏发育的环境污染物，心脏发育是大多数动物胚胎发育的关键步骤。迄今为止，对于暴露于这些污染物的鱼类中观察到的心脏缺陷的分子机制知之甚少。文献表明，PCBs 和 TCDD 引起的心脏缺陷与 cyp1A 的表达同时发生，但不是由其引起，这是由于芳烃受体 (AhR) 基因激活途径的激活。然而，在这项研究中，对暴露于 PCBs 和 TCDD 的鱼类心脏进行的详细可视化显示，除了早期心脏发育中心脏环化的失败外，心脏的内心内膜层也无法维持适当的细胞黏附和组织完整性。这导致斑马鱼和大西洋鲟鱼的心内膜和心肌之间出现间隙，表明内皮细胞黏附连接形成存在功能缺陷。因此，我们使用免疫组织化学方法来探索触发心脏缺陷的分子机制，以确定关键调节和黏附分子的位置和磷酸化状态。我们假设 PCB 和 TCDD 激活 AhR，使 Src 磷酸化，然后使内皮细胞黏附连接蛋白 VEcadherin 磷酸化。当磷酸化时，在内膜和脉管系统中发现的 VEcadherin 二聚体分离，从而降低组织完整性。在斑马鱼中，用 PCB 和 TCDD 污染物处理会导致心脏组织中 VEcadherin 的磷酸化程度更高，这表明这些细胞的连接性降低。Src 磷酸化的小分子抑制可防止污染物刺激的 VEcadherin 磷酸化，并挽救心脏功能和大体形态。大西洋鲟鱼心脏在组织水平上与暴露于污染物的斑马鱼心脏表型相似。这些数据表明，PCBs 和 TCDD 在心脏中的作用机制部分不同于文献中描述的经典机制，并且心脏缺陷受到这种非基因组机制的影响。
