Centro Interdisciplinar de Investigação Marinha e Ambiental (CIIMAR), 4450-208 Matosinhos, Portugal.
Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, 4200-135 Porto, Portugal.
Int J Mol Sci. 2022 Oct 18;23(20):12475. doi: 10.3390/ijms232012475.
The present work aimed to study the role of dietary tryptophan supplementation in modulating the European seabass () immune condition during stressful rearing conditions (i.e., 15 days exposure to high density), as well as the immune response to acute inflammation after intraperitoneal injection of a bacterial pathogen. Stress alone did not compromise seabass health indicators. In contrast, a clear peripheral and local inflammatory response was observed in response to the inoculated bacteria. Moreover, exposure to a high stocking density seemed to exacerbate the inflammatory response at early sampling points, compared to fish stocked at a lower density. In contrast, stressed fish presented some immune-suppressing effects on the T-cell surface glycoprotein receptor expressions at a late sampling point following inflammation. Regarding the effects of dietary tryptophan, no changes were observed on seabass immune indicators prior to inflammation, while a small number of immunosuppressive effects were observed in response to inflammation, supporting tryptophan's role in the promotion of immune-tolerance signals during inflammation. Nonetheless, tryptophan dietary supplementation improved the inflammatory response against a bacterial pathogen during stressful conditions, supported by a reduction of plasma cortisol levels, an up-regulation of several immune-related genes at 48 h, and an inversion of the previously observed, stress-induced T-cell suppression. Finally, the involvement of tryptophan catabolism in macrophages was confirmed by the up-regulation of genes involved in the kynurenine pathway. The present study brings new insights regarding the immune modulatory role of tryptophan during stressful conditions in fish, thus allowing for the development of novel prophylactic protocols during vaccination by intraperitoneal injection in the European seabass.
本研究旨在探讨膳食色氨酸补充在调节欧洲鲈鱼（）应激养殖条件（即 15 天高密度暴露）下免疫状态中的作用，以及在腹腔注射细菌病原体后对急性炎症的免疫反应。单独的应激不会损害鲈鱼的健康指标。相反，在注射细菌后观察到明显的外周和局部炎症反应。此外，与低密度饲养的鱼类相比，高密度饲养似乎会在早期采样点加剧炎症反应。相比之下，应激鱼在炎症后晚期采样点对 T 细胞表面糖蛋白受体表达表现出一些免疫抑制作用。关于膳食色氨酸的影响，在炎症发生前，色氨酸对鲈鱼的免疫指标没有变化，而在炎症反应中观察到一些免疫抑制作用，这支持了色氨酸在促进炎症过程中免疫耐受信号方面的作用。尽管如此，在应激条件下，色氨酸的饮食补充改善了对细菌病原体的炎症反应，这得益于血浆皮质醇水平的降低、48 小时时几种免疫相关基因的上调，以及之前观察到的应激诱导的 T 细胞抑制的逆转。最后，通过上调参与犬尿氨酸途径的基因，证实了色氨酸分解代谢在巨噬细胞中的作用。本研究为鱼类在应激条件下色氨酸的免疫调节作用提供了新的见解，从而为通过腹腔内注射在欧洲鲈鱼中进行疫苗接种开发新的预防性方案提供了依据。
