Hif-1α/Hsf1/Hsp70 signaling pathway regulates redox homeostasis and apoptosis in large yellow croaker (<i>Larimichthys crocea</i>) under environmental hypoxia
Shengyu Luo, 宁波大学海洋学院教育部应用海洋生物技术重点实验室, 浙江 宁波 315211, 中国, Jingqian Wang, Cheng Liu, Xinming Gao, Yibo Zhang, Jie Ding, Cong-Cong Hou, Junquan Zhu, Bao Lou, Weiliang Shen, Xiongfei Wu, Chundan Zhang, Daojun Tang, 浙江省农业科学院, 浙江 杭州 310021, 中国, 宁波市海洋与渔业研究院大黄鱼育种国家重点实验室, 浙江 宁波 315012, 中国
Abstract
Oxygen is an essential molecule for animal respiration, growth, and survival. Unlike in terrestrial environments, contamination and climate change have led to the frequent occurrence of hypoxia in aquatic environments, thus impacting aquatic animal survival. However, the adaptative mechanisms underlying fish responses to environmental hypoxia remain largely unknown. Here, we used large yellow croaker (<i>Larimichthys crocea</i>) and large yellow croaker fry (LYCF) cells to investigate the roles of the Hif-1α/Hsf1/Hsp70 signaling pathway in the regulation of cellular redox homeostasis, and apoptosis. We confirmed that hypoxia induced the expression of Hif-1α, Hsf1, and Hsp70 <i>in vivo</i> and <i>in vitro</i>. Genetic <i>Hsp70</i> knockdown/overexpression indicated that Hsp70 was required for maintaining redox homeostasis and resisting oxidative stress in LYCF cells under hypoxic stress. Hsp70 inhibited caspase-dependent intrinsic apoptosis by maintaining normal mitochondrial membrane potential, enhancing Bcl-2 mRNA and protein expression, inhibiting <i>Bax</i> and <i>caspase3</i> mRNA expression, and suppressing caspase-3 and caspase-9 activation. Hsp70 suppressed caspase-independent intrinsic apoptosis by inhibiting nuclear translocation of apoptosis-inducing factor (AIF) and disturbed extrinsic apoptosis by inactivating caspase-8. Genetic knockdown/overexpression of <i>Hif-1α</i> and dual-luciferase reporter assay indicated that Hif-1α activated the <i>Hsf1</i> DNA promoter and enhanced <i>Hsf1</i> mRNA transcription. Hsf1 enhanced <i>Hsp70</i> mRNA transcription in a similar manner. In summary, the Hif-1α/Hsf1/Hsp70 signaling pathway plays an important role in regulating redox homeostasis and anti-apoptosis in <i>L. crocea</i> under hypoxic stress.