The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, PR China.
The Key Laboratory of Mariculture, Ministry of Education, Ocean University of China, Qingdao 266003, PR China.
Sci Total Environ. 2021 Nov 10;794:148731. doi: 10.1016/j.scitotenv.2021.148731. Epub 2021 Jun 28.
Hemocytes are critical to the immune defense system of bivalves, and polycyclic aromatic hydrocarbons (PAHs) can mediate the immunity of bivalves by affecting the apoptosis of hemocytes. However, the underlying mechanism is still unclear. Chlamys farreri, as an important economic bivalve, was selected as the research subject for this experimentation. The hemocytes were exposed to typical PAHs-benzopyrene (B[a]P) in vitro to explore the apoptosis mechanism through detecting oxidative stress and oxidative damage-related indicators, apoptosis pathway factors, and apoptosis rate within 24 h. The results showed that the reactive oxygen species (ROS) and benzo[a]pyrene-7,8-diol-9,10-epoxide (BPDE) content in hemocytes increased significantly under B[a]P exposure, while antioxidant genes, glutathione peroxidase content and total antioxidant capacity all showed a trend of first rising and subsequent falling. B[a]P also caused serious damage to DNA and lysosomal membrane stability. The proapoptotic factors genes in the mitochondrial apoptosis pathway were significantly up-regulated, and the anti-apoptotic gene Bcl-2 was significantly down-regulated. Besides, mitochondrial membrane potential stability was significantly reduced and caspase 9 enzyme activity was significantly improved with the B[a]P stimulation. The factors of death receptor pathway were also significantly up-regulated by B[a]P. Moreover, the expression levels of Mitogen-Activated Protein Kinases were also induced. The gene expression and enzyme activity of the caspase 3 and the apoptosis rate were significantly increased under B[a]P exposure. In conclusion, these results indicated that ROS was induced by B[a]P, and further triggered the oxidative stress and oxidative damage in hemocytes. B[a]P induced hemocyte apoptosis was mediated by both mitochondrial apoptosis pathway and death receptor apoptosis, and the activation of mitochondrial apoptosis pathway was affected by ROS. In addition, BPDE and MAPKs may play important roles in the B[a]P-mediated apoptosis pathway. This study deepens understanding of the apoptosis pathway and the immunotoxicity mechanism in bivalves hemocytes stimulated by persistent organic pollutants.
血细胞对于双壳贝类的免疫防御系统至关重要，多环芳烃（PAHs）可以通过影响血细胞凋亡来调节双壳贝类的免疫功能。然而，其潜在机制尚不清楚。栉孔扇贝作为一种重要的经济贝类，被选为本实验的研究对象。通过体外暴露于典型的 PAHs-苯并[a]芘（B[a]P），在 24 小时内检测氧化应激和氧化损伤相关指标、凋亡途径因子和凋亡率，以探讨其凋亡机制。结果表明，B[a]P 暴露后血细胞内活性氧（ROS）和苯并[a]芘-7,8-二醇-9,10-环氧化物（BPDE）含量显著增加，而抗氧化基因、谷胱甘肽过氧化物酶含量和总抗氧化能力均呈现先上升后下降的趋势。B[a]P 还对 DNA 和溶酶体膜稳定性造成严重损伤。线粒体凋亡途径中的促凋亡因子基因显著上调，抗凋亡基因 Bcl-2 显著下调。此外，B[a]P 刺激导致线粒体膜电位稳定性显著降低，caspase 9 酶活性显著提高。死亡受体途径的相关因子也被 B[a]P 显著上调。同时，B[a]P 还诱导了丝裂原激活蛋白激酶的表达。B[a]P 暴露后，caspase 3 基因表达和酶活性以及凋亡率均显著升高。综上所述，这些结果表明 B[a]P 诱导 ROS 产生，进而引发血细胞内的氧化应激和氧化损伤。B[a]P 诱导的血细胞凋亡是通过线粒体凋亡途径和死亡受体凋亡途径介导的，而线粒体凋亡途径的激活受 ROS 影响。此外，BPDE 和 MAPKs 可能在 B[a]P 介导的凋亡途径中发挥重要作用。本研究加深了对双壳贝类血细胞中持久性有机污染物诱导凋亡途径和免疫毒性机制的理解。
