Department of Anatomy, Faculty of Health Sciences, University of Pretoria, Private Bag x323, Arcadia, 0007, South Africa.
Laboratory for Microscopy and Microanalysis, University of Pretoria, South Africa.
Environ Toxicol Pharmacol. 2019 Jul;69:86-94. doi: 10.1016/j.etap.2019.03.021. Epub 2019 Mar 28.
Environmental presence and human exposure to heavy metals in air and cigarette smoke has led to a worldwide increase in respiratory disease. The effects of oral exposure to heavy metals in liver and kidney structure and function have been widely investigated and the respiratory system as a target is often overlooked. The aim of the study was to investigate the possible structural changes in the lung tissue of Sprague-Dawley rats after oral exposure for 28 days to cadmium (Cd) and mercury (Hg), alone and in combination at 1000 times the World Health Organization's limit for each metal in drinking water. Following exposure, the general morphology of the bronchiole and lungs as well as collagen and elastin distribution was evaluated using histological techniques and transmission electron microscopy. In the lungs, structural changes to the alveoli included collapsed alveolar spaces, presence of inflammatory cells and thickening of the alveolar walls. In addition, exposure to Cd and Hg caused degeneration of the alveolar structures resulting in confluent alveoli. Changes in bronchiole morphology included an increase in smooth muscle mass with luminal epithelium degeneration, detachment and aggregation. Prominent bronchiole-associated lymphoid tissue was present in the group exposed to Cd and Hg. Ultrastructural examination confirmed the presence of fibrosis where in the Cd exposed group, collagen fibrils arrangement was dense, while in the Hg exposed group, additional prominent elastin was present. This study identified the lungs as target of heavy metals toxicity following oral exposure resulting in cellular damage, inflammation and fibrosis and increased risk of respiratory disease where Hg showed the greatest fibrotic effect, which was further, aggravated in combination with Cd.
环境中空气和香烟烟雾中的重金属的存在以及人类对此的接触，导致了全球范围内呼吸道疾病的增加。人们广泛研究了重金属经口服暴露对肝脏和肾脏结构和功能的影响，而呼吸道系统往往被忽视。本研究的目的是调查 Sprague-Dawley 大鼠经口服暴露于饮用水中重金属（Cd 和 Hg）含量分别为世界卫生组织限量的 1000 倍时，28 天后肺部组织可能发生的结构变化。暴露后，采用组织学技术和透射电子显微镜评估了细支气管和肺部的一般形态、胶原蛋白和弹性蛋白的分布。在肺部，肺泡空间塌陷、炎症细胞存在以及肺泡壁增厚等结构变化。此外，Cd 和 Hg 的暴露导致肺泡结构退化，出现融合的肺泡。细支气管形态的变化包括：腔上皮退化、分离和聚集导致平滑肌质量增加。暴露于 Cd 和 Hg 的组中，存在明显的细支气管相关淋巴组织。超微结构检查证实存在纤维化，其中 Cd 暴露组胶原纤维排列密集，而 Hg 暴露组则存在更多明显的弹性蛋白。本研究表明，经口服暴露后，重金属毒性的靶器官为肺部，导致细胞损伤、炎症和纤维化，增加了患呼吸道疾病的风险，其中 Hg 表现出最大的纤维化作用，与 Cd 联合暴露时作用进一步加剧。
